TribloO.com's SCUBA diving dictionary from and for divers: from beginners to advanced, you've got it all!
It is one of the dives comprised in the PADI Advanced Open Water course and can count as credit towards any diving specialty course.
It's when you're heading off, well prepared, kitted and donning a dry suit, to dive mountain lakes, ready to face one-degree temperatures and endure longer deco stops. Guaranteed thrill! Any diving ranging from 300m above sea level to 3000m or so qualifies for altitude diving. Above that, let's be honest, it is rare to find water in liquid form... so maybe you should take up ice-skating rather than SCUBA!
BCD or jacket/vest
The BCD (Buoyancy Control Device), or BC (Buoyancy Compensator) or even just jacket or vest, is the instrument which your tank is strapped onto. It's all in the name. The BCD allows you to stabilize yourself and have control over your buoyancy and position in the water during the descent or ascent. It's also very handy for storing a few tools (slate, reel, torch, etc.)!
Boyle’s Law is certainly the most important physical law to grasp when you’re learning to dive (and even well after!). It connects the pressure to the volume of gas and can be explained rather simply. The deeper we go underwater, the more the pressure, which is a weight, increases. When you come up, the pressure decreases. Moreover, the more the pressure increases, the more the volume of gas, e.g. air, decreases and vice versa. Simple, yeah?
This law is really central to diving because it governs:
- What happens in your ears and mask, hence the need to equalize, especially when you descend. During the ascent, the air increases or expands and escapes by itself.
- What happens in your jacket or BCD in order to master your buoyancy and reach the sacrosanct neutral buoyancy. During the descent, you need to slowly and steadily add air in your BCD so that you don’t sink like a stone. During the ascent, you need to progressively remove air from you BCD so that you don’t torpedo up. Basically, you need to keep a certain volume of air in your jacket to stay more or less neutral.
- What happens with the nitrogen absorbed by your body, in association with Henry’s law and the exchange of gas when it comes in contact with liquid.
Breathing rates and air pigs
You've probably seen this before: as you're a third into your air tank, someone in the group is already reaching the reserve at 50 bars! Yes, there are ones that use it all up early, even in diving! How much air one has left in their tank after a dive is one of the most talked about issues in dive centers worldwide! Who's got more! Who's hogging up air! Who's used up the least! Bla-bla-bla! We don’t have to tell you, you all know the story. It can actually be stressful to some and make people feel cast out of the group, so try and be considerate!
Two important facts: 1) girls tend to use less air than boys and 2) 'bigger' people tend to breath a bit more than smaller people. These are general considerations and do not reflect particularities in people. Here are a few tips to help you out:
- Stay relaxed and chill, don't force your breathing—breathe naturally
- Building up experience and logging more and more dives will ease things up. NB: beginners most often see their air consumption decrease over time!
- If you stay hydrated, rested, and fit your body will need less air for a given task
- Try and breathe out slightly longer than you breathe in: you'll get rid of carbon dioxide, the gas responsible for your accelerated breathing rate, and empty out the 'dead air spaces' properly. For example, on your next dive try to pace your breaths counting in your head: '2 seconds in, 3 seconds out' is good to start with. Little by little this will become natural and soon you'll be sorted!
- Pay no attention to those showboating and stay natural!
Now, let’s look at some figures for breathing rates: under 11 liters per minute you are doing good—we an even say very good; 15 to 20 liters per minute, you like your air a tad too much; over 21 liters per minute, you're actually starving for air and there's little chance your dive will last more than 35 minutes.
World Underwater Federation (CMAS) comprises over 130 federations from 5 continents. Founded in 1959, CMAS is the first global organization for diving as well as the first organization to truly structure scuba diving instruction. In addition to being a major player in the organization of international underwater sporting events, the CMAS also participates actively in technical and scientific research and development. It is one of the oldest training systems for diving. For fans of “old school” learning, CMAS provides courses of exemplary quality and professionalism. Most importantly, each training course gives you the right to a CERTIFICATE VALID IN ALL DIVING CENTERS AROUND THE WORLD.
In caves, everything seems limited: your visibility is sometimes limited or turbid, movement is limited, breathing time is limited, and number of people is limited… Everything limited! Except for the thrill! What a sensation! Being in fresh or salt and pure water! Witnessing unbelievable plays of color! Exploring extraordinary vaults! And much more!
Contrary to caverns, caves allow you to go further in the rock where you lose sight of the light, point of entry, and way out! In caves, we leave that all behind us!
What you’ll need: a special line reel with several hundred meters of wire, 2 lights per diver, a cucumber cool attitude, and a good dose of self-control.
Cave diving is reserved for groups of avid and highly experienced thrill-seekers, very often Tec divers with a specialty in caves or spelunking.
For recreational divers, cavern diving is a good way to begin to discover diving in a closed, overhead environment and learn basic techniques, such as the perfect neutral buoyancy, the frog kick, how to use a light, etc. The cavern implies several things:
- You’re diving in a semi-closed space where you have no direct vertical access to the surface
- You see the light of your entry and exit point at any given moment
- You generally have less than 40 meters to go to reach the surface
Remember, once you’re certified for caverns, the next step is cave exploring!
Cenotes are cave systems of freshwater sanctuaries and Mayan sacred wells. The most spectacular are found in the Yucatan Peninsula in Mexico where cave diving enthusiasts literally flock. Cenotes contain strangely varied fauna or the lack thereof. Conditions are between fresh and saltwater and temperatures a mix of tropical and ‘cold’. For the most part, cenotes are located right in the middle of a jungle, but sometimes you can find them only a few meters from the ocean. Take our word for it, there’s nothing like them!
SCUBA diving is not only about having fun and fish spotting. In fact, some divers work underwater! By work, we mean construction work, i.e. cutting beams and tubes, slicing concrete, building up pillars, backfilling, welding, and checking structural integrity of buildings, so yeah, a world away from the leisurely recreational dive realm! A Commercial Diver is someone who builds bridges, marinas, locks, and oil platforms. He/ she also fixes underwater cables, pipelines, and aqueducts as well as checking and cleaning underwater structures and ships. This person is essentially an underwater worker and engineer able to work in both fresh and salt water!
Achtung baby: this can be a (very) risky occupation. To become a Commercial Diver you must take a specific training that is both strenuous and expensive. However, once certified and with a few assignments and specializations under your belt, believe us, your salary will start to show a few more digits than most of your friends’!
Stuffy nose the day of your dive? Not to worry (too much)! Rinsing out your nose and sinuses with salt water is very effective before diving. However, nasal irrigation is only good for light congestion, a.k.a. a simple head cold, to facilitate the descent and the equalization of the ears. If the cold is a nasty one, the ascent will be a nightmare and may even result in a reverse block and ruptured eardrums. Easy as: DO NOT DIVE with a serious cold! Raincheck it. Also, please note, powerful decongestants like Sudafed should be avoided, especially if you’re using Nitrox: you run an increased risk of oxygen toxicity.
Ah, the famous compass for divers! Often confused with a GPS, this object that many divers wear around their wrists indicates the direction and not where you actually are. The compass is often victim to many insults! It is set on the boat or on the surface before immersion; however, loses much of its effectiveness if the site topography is hilly or the current is rough. Training is available to master its subtleties, but nothing beats opening your ears and eyes before and during the dive site briefing.
A compass can actually turn into a GPS if you combine its use with natural navigation. The latter is none other than observation of dive maps prior to and during your dive, and recognizing noteworthy elements, i.e. a wall, a coral head, the sun, the current, etc. Once again, experience and accumulation of dives in various environments are the real keys to developing your navigation skills. And if all else fails, there are always the guides who can show you the way and get you back to the boat!
For more infos on underwater navigation training:
Coral reefs are one of the richest eco-systems on the planet! It is literally a hard limestone structure that is home to diverse flora and fauna ranging from microscopic to enormous. There are thousands of colors and shapes to be found on a reef and the diversity of life is simply stunning! Coral reefs can only exist and thrive in quite narrow ranges of salinity, temperature, and light exposure. Above all, the water must be 'warm', i.e. from 23-30° C, and the sunlight must stay consistent throughout the year. Hence the fact that you only find coral reefs around the equator!
Put simply, a coral reef consists of millions of little mouths, or polyps, that look like upside down jellyfish! Those polyps feed on the floating particles, plankton, and sunlight, thus producing oxygen through photosynthesis. It is true but unfortunately, not much talked about and/or publicized that coral reefs, marine or river algae, and plankton produce over 70% of the oxygen we breathe! Yes, 70%! So, although they're less visible than the Amazon forest, they are just as vital to us and to life on Earth. Therefore, coral reef protection and conservation is absolutely crucial to our survival and the survival of all marine life!
Moreover, this rich ecosystem feeds a large variety of fish, both herbivores and carnivores, as well as serving as shelter for some fauna and a retainer for a lot of low lying islands and their beaches. As a matter of fact, without reefs, the currents, the surf, and the swell can gradually and wholly erode a beach making all those paradise islands we crave so desperately disappear. And, to take it one step further, coral reefs even help build those beaches we love so dearly. Take, for example, the parrotfish. These colorful fish feed on the reefs’ polyps and as they are munching on the coral they also take a lot of limestone with them. In their stomachs, the limestone and the nutritive bits are grinded and sorted leaving only the nutrients to be digested. The rest is simply 'pooped out' and will end up on the nearest island contributing to the shaping of the beach! Try not to think about this as you’re taking your next romantic beach walk. What you're walking on has passed through a parrotfish to put it mildly-- ewww!
This is when water-- driven by tides, winds, and the topography of the region-- moves all by itself! We can either go with it—drift diving—or handle it in another manner: start your dive against the current sticking to the bottom or walls as close as you can to have a ‘light’ current and when you arrive at the end of the site (or at half tank or you’re getting tired), turn around and let the current take you back to the boat. The current is basically regular at a certain depth and your guide will make sure you’re in the right place to avoid any unwanted surprises, i.e. one or more divers getting carried farther out from the reef into the blue, etc. Nevertheless, there does exist areas where there is a downdraft. These areas are super dangerous and you must stick to the wall and follow your guide’s orders to the letter! The same goes for the updraft, which can easily speed up your ascent rate—a real problem if you have mandatory decompression stops to do.
We measure currents in knots:
- 1-3 knots: light to medium current. Possible to go against, no problem, with a small cost of energy and air.
- 4-5 knots: strong current. Swimming against is strongly discouraged. To get out, a strong freestyle across the current is necessary, but you have to decide early because you risk using up your air supply real fast.
- More than 6 knots: extremely strong current. Make sure your guide sees you at all times. Your bubbles are no longer vertical. Most of the fauna is out of sight; only tuna, bonitos, jacks, and certain sharks are out!
DIve torch or light
When your underwater world has plunged into the darkness, it is high time for you to switch on the dive light or dive torch! This little accessory is absolutely crucial during night dives and can also come in quite handy on wreck and cave diving. You can even use it to just add a little color to your dives. Finally, when visibility becomes (really) low, the guide or leader may use one to provide a reference point to divers. Among all diving accessories, this one is high up on the must-have list!
DPV, or underwater scooter
Feeling too lazy to fin? With the underwater scooter, or DPV (for Diver Propulsion Vehicle), you'll enjoy being towed around underwater at a reasonable speed. Try diving against the current, and covering long distances while carrying lots of tanks (Tec divers) without wasting energy against the drag: it is now possible! Though to be as agile and graceful as James Bond you'll first need to learn the basic safety rules and techniques. Sign up for a specialty training and get some practice. It's real fun! Call me Bond. James Bond.
Who knew bubbles could be dangerous or, in some cases, fatal? Decompression sickness is due to improper elimination of nitrogen that dissolves in the body then transforms into microbubbles. These microbubbles become increasingly large and start blocking the blood vessels that transport oxygen to your limbs and organs, the rest of your body and, most importantly, your brain. To avoid this, you must stay hydrated, not dive when sick or tired, not drink alcohol during the surface interval (SI), maintain a slow ascent rate (approx. 15 meters/minute), totally respect the decompression stops, always perform a 3-minute safety stop at 5 meters, and do not do anything strenuous after your dive. And finally, to completely eliminate any risks, wait a minimum of 12 hours post-dive before taking a plane.
Whether diving with a guide or autonomously, for each certificate there is an allowed depth or depth standard. During your training, you are taught to dive up to a precise depth, a.k.a. your depth limit or comfort zone. Those set depths aren't chosen randomly! You do need to respect those limits since the guide or instructor leading you through the post-training fun dives won't be holding your hand the whole time and won't have time to remind you a hundred times to level up. Also, you're an adult with full control over your decisions and need to take responsibility for your actions. If you are working with a dive computer or a digital depth gauge, it won't be the guide's fault if you overshoot your depth limit—it will be yours!
What's more, as we've already said, your guide can't forever prevent you from going beyond your depth limit; therefore, if an accident should occur and you're out of your authorized depth, your insurance won't cover you. By all means, we wouldn't wish that on anyone! So, please, we can’t say it enough, act responsibly and stay within your depth standards or allowed limits!
Mac or PC? Big debate no question, but here the question is rather between SUUNTO, MARES, UWATEC, CRESSI, OCEANIC, LIQUIVISION, etc ... Sign of recognition amongst divers, even out of the water, the computer can optimize your dive time by automatically calculating the time remaining before you need to start your decompression stops—these are mandatory unlike safety stops which are just “highly recommended”. The computer calculates all the parameters of your dive(s) to the second and within 10 cm… the table time is revolutionized! They come in all shapes, sizes, and colors. Some deal with only Nitrox and air while others can compute a dozen different gas mixtures!
Today, this instrument is a must for any diver who respects him / herself and his / her buddy. Dive with peace of mind, manage your parameters yourself, and, icing on the cake, no need for an antivirus!
Diving, like many adventure sports, requires you to be insured or at least covered for civil liability (included automatically with your FFESSM, French diving federation, permit or when you reserve with a Mastercard GOLD or Visa Premier). This covers you if another diver sues you. In addition to the mandatory civil liability insurance, a supplementary insurance covering you against personal risks related to diving is strongly recommended. These could include accidents, medical bills, search teams, repatriation, etc. The main insurers are:
- Assurance Loisir with FFESSM and Cabinet Lafont (specialized in French diving)
- DAN: THE major player in dive insurance
- Aqua Med (widespread in Germany and Switzerland)
- PADI Professional Dive Insurance
Look at you! Rambo of the ocean! The bigger it is, the happier the men are although the women just don’t seem to get it. And, you know what? The girls are right! The dive knife has very little use. The few exceptions:
- Spearfishing: in order to scrape off edible shellfish and other seafood or to remove the harpoon from the fish
- Cut off fishing lines from reefs
- Extreme emergencies, e.g. a fellow diver stuck and you need to cut him loose
There you have it ladies and gentlemen, the main uses for a knife when diving. So, a small, discreet, simple knife will do. Word to the wise, having a machete as long as your forearm only proves one thing…
Form and design, volume, field of vision, and color of silicone, these are the 4 criteria that enable you to see underwater. One thing is sure, your mask’s glass MUST say Tempered or Temp or just simply T. This is a safety standard that you shouldn’t deviate from.
- For vision, one-window masks offer a clear field of vision. Large masks allow you more peripheral. Smaller masks require you move your head more for a wider field of vision.
- For comfort, a silicone skirt is highly recommended. Everything else, i.e. cheap masks, damages quickly and is not (at all!) comfortable.
- For volume, only when freediving and spearfishing do you need a low-volume for easy clearing and alleviate compression from the mask on the face. Advanced divers tend to choose low-volume masks while beginners opt more for higher volumes. But, you must remember, comfort trumps everything!
Finally, the joy for divers lies in the details: black or clear skirt, high or low-volume, frames or frameless—there is something for everybody depending on your expectations and needs.
To know if a mask is made for your face, there is nothing simpler: put it on your face and loosen up face—you shouldn’t be carrying any tension! Brush back your hair from your forehead and try to have no or little mustache. Breathe in through your nose and hold your breath. Slowly lower your face and look at the ground. If the mask doesn’t fall off your face, then it’s definitely the mask for you! When you resume breathing the mask will fall.
The vast majority of masks are made for all shapes and sizes, it is EXTREMELY rare to not be able to find a mask that’s right for you!
- Do not over tighten (if at all) your mask on your face. The mask is shaped to ensure water resistance, if you tighten too much, you deform your mask and it loses its primary function.
- If your face is relaxed and perfectly normal, water will not get in your mask. If you tense up or smile water will get in, it’s that simple.
- If you have a mustache, as long as it does not exceed a few millimeters, you’re ok. A big mustache will let water in. To overcome this, i.e. if you want to keep your stache, apply a layer of fatty-based paraffin (Vaseline) on it and make sure it stays on until the end of your dive. If not, shave and it’s all good!
- Choose a neoprene mask strap—more comfortable, easier to adjust, and it doesn’t pull on your hair!
Swimming for hours like a fish in water is only possible through the use of a steel or aluminum tank. This is your compressed gas reservoir. It is usually air, but can also be Nitrox or Trimix—this last one is with helium! First of all, no one dives with pure oxygen so it is really an air tank. In aluminum, the tank has negative buoyancy when full becoming gradually positive as it empties out; therefore, you must adjust its buoyancy accordingly! With steel, the buoyancy doesn’t change—or very little--, so the tank has negative buoyancy whether its empty or full!
For divers with thick wetsuits or drysuits, it is preferable to use steel tanks in order to be lighter on their weight belt. For thin or shorty wetsuits, the pick is aluminum.
There are tanks of all sizes and volumes. The most common is the 12 liter tank. For divers that are more air thirsty, you can go for 15 or even 18L tanks. Also for small sized divers, kids, or Tec divers who need external decompression tanks (also called stages), there are 5, 6, 7, and 8L tanks.
If one loads you up with weight-- either on your belt or in your BCD-- prior to a dive, it's not because they are being mean, it’s simply to cancel out the positive buoyancy of your wetsuit, your body, and the saltwater. Basically, if you’re going out SCUBA diving, it's way better to get under the water rather than bounce around on the surface, right? Be careful to optimize your weighting so you don't have to compensate too much, i.e. an over-weighted diver will struggle to keep a horizontal position and not sir-up the bottom or, worse, break the coral whereas an under-weighted diver will waste a lot of energy trying to stay down and not constantly shoot back up! Check before and after your dive with this very simple technique: on the surface with the regulator in your mouth, straight up and vertical in water that is too deep to stand, without finning, empty your BCD out whilst drawing a breath; hold it for a few seconds; then calmly exhale and you should start, slowly but surely. Tada!
Diving liveaboard is a SCUBA diving cruise where you don’t go back to the dive center after each dive or even at the end of the day. You live on the boat for several days, hence the name live aboard!
This is a great way to enjoy the region and is reserved for advanced level divers who are looking for a little off-the-beaten-track adventure. Remote areas become accessible like Raja Ampat, the Galapagos, the Similan Islands, Fiji, and even the Great Barrier Reef, and you get to live a truly awesome experience!
Dolphins are marine mammals and global symbols of super human intelligence. They are also super sweet animals and like us, have lungs so must hold their breath when swimming underwater. They can stay 15 minutes underwater and go as deep as 300 meters. They vary greatly in size according to the species, e.g. Maui’s dolphin measures on average 1.7 meters long where as the Tursiop or Bottlenose, a.k.a. Flipper, can reach up to 4 meters! The latter has been seen jumping up to 6 meters high! In fact, they jump over waves to go faster and save energy either because it’s fun or because they’re in love! Dolphins can also be seen at the bow of your boat where they let themselves get “pushed” around by your boat—their way of playing. Finally, they are exceptional swimmers that love company from fellow dolphins, people, and being free.
Diving areas where they can be spotted most frequently and most regularly either as few or in a large group of up to 500 are often also heavily populated by divers and non-divers. We set out a few do’s & don’ts for you:
- Don’t chase them! Let them come to you.
- Do leave them in liberty. Don’t try and touch them
- When in a boat, don’t go at them
- If there are young and/or babies present, don’t get in the water with them—adults will protect the offspring
- If near the coast or a cliff, don’t corner them. Do leave them a way out.
- Do enjoy the moment with your eyes and your heart before flashing endless snaps of them.
Like a message in a bottle, let yourself drift with the current and enjoy a dive where you don’t have to swim (too much). Such a great sensation going great distances and exploring sites with such little effort! But, be careful not to let yourself get too carried away. Alone, orientation is not innate and once back on the surface, hello Mr. Nightmare! Drift diving is always with a guide (more than one is even better), a reel, a SMB, and a boat or in some cases just a safe solid surface.
The main interest of drift diving is basically to see “big ones”, i.e. pelagic fish and predators in their natural environment. In fact, strong current areas create the best occasion to see the “big ones” hunting the “little ones” that are struggling to swim against the current to safety. Similarly, the pelagic fish can ventilate (breathe) with less effort facing the current. Some drift diving in French Polynesia, Indonesia, etc. requires a certain amount of experience. Don’t hesitate to sign up for classes:
More infos on drift diving courses and training:
Get ready to comfortably enter waters less than 16°C! The drysuit is an integral garment designed especially for cold water and long, deep dives that completely protects you from water and therefore, from the cold! This is extremely important and essential because the body cools down 20 times faster in water than in open air.
There are two types of drysuits:
- Neoprene, 4-7mm thick with a zip up the back. This type of suit provides good thermal insulation, but has a significant amount of positive buoyancy
- Trilaminate, very popular with Tec divers due to its lightness and strength. You also have the option of adapting your layers according to the season, temperature, etc.
Remember to always adjust your weight because drysuits carry a large volume of air!
As you’re going down, learn to balance your ears and take your time, the two secrets for beginning your dive and staying relaxed. The idea is to add air in your ears to equalize the pressure on the two sides of your eardrums. This way, the small volume of air in your ears is constant and all goes ‘down’ well!
Hold your nose and blow gently several times while leaning your head to the right to equalize the left ear and repeat for the other side. This maneuver is the most common and is called Vasalva. You can also slightly push out your lower jaw and move it from one side to the other. Finally, for some people just simply swallowing your own saliva works. All these techniques can be combined or one after the other as long as you do them gently and don’t force anything. If nothing seems to work, go back up and try again! Just don’t force it!
Equalization is a delicate subject for many, especially beginners. The more relaxed, confident and patient you are taking one thing at a time, the better you’ll be. The first few meters are the most important. Once past 10-12 meters, equalization becomes easier.
Fédération Française d’Etudes et de Sports Sous-Marins is a French diving school in France and international. It provides rigorous and quality training that was initially… military training.
The validation and certification system for the FFESSM is inline with that of CMAS: a diver has 1-4 stars or levels and an instructor 1-3.
However, the prerogatives differ from PADI. With FFESSM, there is no clear distinction between a recreational and technical dive even if one has never to go through big decompression stops. The following gives you an idea of the levels:
- Level 1: diver can dive autonomously (DA), i.e. without professional guide or at least level 4 diver, at up to 10 meters and supervised (DS) up to 20 meters
- Level 2: DA at 20 m and DS at 40 m
- Level 3: DA at 40 m and DS at 60 m
- Level 4: DA at 60 m
FFESSM delivers DIVING CERTIFICATIONS THAT ARE VALID IN EVERY DIVE CENTERS AROUND THE WORLD.
In the land of penguins, everyone finds the shoe fits:
- Flipper slipper fin or dive slipper that you slip on like a slipper or adjustable ones you can wear with booties. We find them in all shapes and sizes, even cut in half lengthwise (split) or with a bend or with an adjustable sling up the middle. They should be pretty rigid and shorter than those for freediving.
- Fins for freediving are longer and more rigid to increase the propulsion under water, reduce efforts, and thus optimize the time underwater with only a single breath.
- Swimming and snorkeling fins are for a little tour around in the pool, be beautiful in the lap lanes, work on your crawl, have some bodyboarding fun, and observe fish from the surface. Stay with the flexible models.
- Monofins allow you to swim like a dolphin with a single winged fin! Achtung baby, they require a top physical condition and some training. They work particularly well with freediving.
First dive, Discovery dive, or DSD
This is an introduction to SCUBA diving—the best solution for the curious! During this first dive, your dive instructor will explain the basic principles of SCUBA diving and give you an overview of the gear provided by the dive center. Next, your instructor will take you in a pool or shallow waters to help you practice basic diving techniques, such as ear equalization and mask clearing. Then, if you feel ready, always with your instructor, you can make a discovery dive up to 12 meters deep. Most DSDs (Discover Scuba Diving) last one to two hours all included.
If you haven’t already seen the French film Le Grand Bleu from Luc Besson, please do… NOW! You will thank us later. In this film, you discover the beauty of freediving, the sport where you go under the water without a tank, only holding your breath. Anybody can practice freediving as long as they follow certain basic rules, the numero uno being always dive in pairs—never alone. Amateur and professional training courses that enable you to reach unimaginable depths are available through AIDA and SSI.
A ghillie suit is a camouflaged suit used for freedive hunting so that your target does not detect you!
Sometimes when you dive, you cross currents of muddy-like water. Rest assured, it’s not a problem of view! It’s a strange phenomenon that is produced when salt meets freshwater. Basically the mix of salinity muddies up your visibility for a short period.
The following explanation may seem barbaric at first, but actually it is quite simple. Henry’s Law is the physical theory of the solubility of gas... The amount of given gas that dissolves when it meets a volume of liquid to be in equilibrium with that liquid. In SCUBA diving, we breathe air at ambient pressure. Your organism then loads up in Nitrogen under the effect of the pressure. To prevent rapid oversaturation, the diver must come up slowly (approx 15 meters/minute) and make decompression stops if necessary. If not, he/she risks decompression sickness.
Stay within your prerogatives, drink plenty of water, don’t dive when you’re tired, and the gas exchange related to Henry’s Law will go over just fine!
“Hood up”, red light indicators! That means it’s a bit chilly down there and you should get ready for some delicious cold water diving. In fact, we lose most body heat through our head and a small hood is often better than a thicker suit… at least in the beginning.
Just one beer!
Hmmm, a nice cold beer... AFTER the dive! Hits the spot just the way it should, and crowns a good day of diving with your mates and dive buddies. Yes, it's written AFTER because the beer MUST NOT be taken before a dive or in-between dives during the surface interval!
If you're a seasoned diver and have been around a bit, you've probably heard this very phrase: 'Oh come on! It's just ONE beer...' Well, it's unfortunately already too much! SCUBA diving is an adventure sport that calls for a well hydrated body (and alcohol dehydrates) and a clear head (and... well you know what alcohol does to your head, don't you?). So drink responsibly after your day's diving is done... unless you have a night dive of course!
As a sponge naturally absorbs water, light can also be absorbed. The deeper you go, the less light there is. It’s an immutable fact. The opposite would mean you found an underwater city inhabited up to now by an unknown species or that you fell on a pile of phosphorescent jelly!
The light spectrum loses its strength and brightness as you go down. It is also why everything appears super colorful within the first 10 meters. In clear water, progressively as we go deeper, we lose warm colors like reds and oranges around 25-30m. At 40m, yellows and greens begin to get weaker, and at +50m cold colors like blues and purples dominate. An underwater light will bring brightness back to the colors of all the flora and fauna. Finally, good to know, at a depth of 200, light doesn’t enter anymore: if you look up to the surface, you will see blackness… well if you actually reach 200m!
The line reel is a safety accessory. It is like a big spool of thread that lets you easily find your way back during a cave or Tec dive when you have reduced visibility and/or a strong current. It’s used to stay in contact with the permanent line and your buddy and to easily find them when exploring with no hesitation or worry. Also regarding Tec diving, it gives you a moment of rest and better control of your ascent and your horizontal position. On the other hand, during drift dives or in the great blue above seamounts, it allows you to hook up your parachute/SMB and thus throw it out at shallow depths (5-20 meters) so that the boat can easily find you. In no case whatsoever when you attach and throw your SMB, should your line reel be attached to your jacket. Always keep it in your hand, ready to let go immediately if you become caught in it to avoid an uncontrolled ascent. The no-frills models—without all those techy features—are usually the most efficient.
If you haven't heard your instructor and guides say a million times 'Do not hold your breath', that probably means you learned diving on another planet! Lung overexpansion is what can happen to you if you hold your breath while diving, more precisely while ascending. We could explain this medical condition in a thousand words, but one striking image may suffice: picture a ballon. Now, what would happen if you blew it up too much-- we're talking way too much? That, my dear friends, is lung overexpansion.
Lycra vs sunscreen
Choose the suit or a Lycra T-shirt over sunscreen any day! Few know this, but the residue from sunscreen gets on and covers corals. Coral needs sun for photosynthesis, the process that gives back vital oxygen to life on Earth! Sunscreen contributes to the proliferation of bad algae, which threaten the whole marine ecosystem and our planet’s atmosphere.
Does this mean the observation of only big fish? Not at all! Actually, it is the all-consuming passion of bio divers or photographs that spend all their time scrutinizing drop-offs and cracks to find the small microorganisms. What irony! In fact, the macro lens used by the photographers to get close-ups of these little critters explains the name. ‘Macro’ diving is therefore focused on the tiny critters that can't fight against any current and are usually camouflaged so you have to really look, scan, scrutinize to see them.
A few examples (list is not by any means exhaustive):
- Shrimps and all kinds of crabs
- Pygmy seahorses
- Most frogfish
There it is, inert and lying at the bottom of the ocean like a heavy stone abandoned by all... except the boats that is! This concrete slab enables them to moor without damaging the seabed by their anchors. This is especially helpful and significant in tropical waters where coral and coral reefs are subject to fast breaks and slow growth. The flora and fauna in temperate environments, often seen as 'encrusting', is much more resistant. Nevertheless, given the systematic and ultimate throwing of the anchor, the mooring line is the most sustainable and environmental friendly solutions!
What’s wet, narrow, long, and in which we submerge ourselves ever so gently? That’s right, a narrow passage. This passage, which is like a tube, is usually found in underwater caves or tight corridors of a shipwreck. Achtung baby: this type of passage requires experience, careful planning, and a cool attitude. And, above all, buddy up and don’t attempt this without adequate prior training.
Neutral buoyancy, a.k.a. the Holy Grail of diving, is the perfect balance underwater enabling you to follow your dive leader with little effort and without degrading the seabed. Also referred to as zero buoyancy, to achieve it gives access to a world where gravity no longer exists: you’re not floating nor sinking, you are really between two waters—light and effective. The recipe is this, one part, master your gear (stab, tank, and weights) and two parts, know your body, especially your breathing.
The more you dive in different environments, the more you use different equipment, and the more experience you gain, the closer you will get to achieving this El Dorado of SCUBA diving techniques. The road may be long. You can take classes through PADI and CMAS under the specialty “buoyancy” to speed up the process on a good solid foundation.
While deep diving, thirty meters deep and beyond, you may start feeling a certain intoxication that can be both scary and exhilarating—you’re feeling nitrogen narcosis, a.k.a. the raptures of the deep, a.k.a. the Martini effect. Your mind goes a little wobbly, and you experience a change in perception, your reactivity, and your decision-making ability get altered a little—you’re not drunk, just euphoric. The ambient pressure explains this phenomenon as nitrogen acts on your neurological connections.
In the case of heavy narcosis and if your abilities are strongly reduced, the remedy is quite simple: go back up to 20-25 meters. When you decrease the pressure, nitrogen ceases to play on your brain and everything becomes clear again.
There is a gradation of narcosis and everyone does not react in the same way. Like alcohol, you build a tolerance with experience, i.e. more and more 30 and 40-meter dives.
- 30 m: “legal” limit of nitrogen narcosis, it is low or very low, but nevertheless present, especially for beginners or people subject to stress or fatigue
- 40 m: average or almost strong narcosis is present; quick reaction, sound decision-making, and logic begin to be impaired
- 45 m: narcosis is strong but still “controllable” with proper training and regular practice of deep SCUBA diving
- 50 m: narcosis is very strong and despite experience, the brain is in slow mode
- 55 m: from here up to 60 m, narcosis is dangerous because decision-making is erratic, slow, and even illogical.
In consequence, divers who go down to over 55-60 m, levels where everyone else suffers narcosis, use a mix of gas with helium to reduce nitrogen narcosis: Trimix.
Nitrox or EAN
Nitrox is an oxygenated air mix with a percentage of oxygen higher than 21%. Nitrox 32 and 36 are the most commonly used. Nitrox 32 means that the gas mixture contains 32% oxygen and 68% nitrogen, instead of the 21 and 79 present in air. Compared to air, use of this gas has the advantage of increasing the time the diver can stay at a given depth. Since there is less nitrogen in Nitrox than in air, its use allows your body to fill up slower with nitrogen and therefore extends your time on the bottom without having to make decompression stops during the ascent. Safety is greatly optimized and you feel less fatigue. Win-win!
More infos on Nitrox courses and training:
Professional Association of Diving Instructors: PADI is an American school of SCUBA diving. It is the most well known and recognized internationally that has democratized SCUBA diving all over the world. The motto here is diving is fun and accessible! PADI offers a wide range of courses for beginners such as DSD for introductory dives and Open Water for level 1, to advanced, such as Master SCUBA diver. It also offers certification for Instructors. The system is divided into two modules: theoretical and practical. After booking your training in a diving center, you can access directly the theoretical part online (e-learning) or with an on-site instructor. As for the practical part, you will first learn in a protected environment like a swimming pool before heading out to sea. At the end of each course and training, you will be issued a CERTIFICATE VALID IN ALL DIVING CENTERS IN THE WORLD.
They are teeny, tiny animals, vegetals or minerals that is practically invisible to the naked eye and passively floats in the water pushed around by the currents. The plankton represents 80% of marine life. Actually, ALL marine life depends on it: from corals to manta rays, whales to some marine birds. Everything is connected and everything comes back! The base in fact.
For those of you who easily get cold underwater, the solution is this: add a wetsuit underneath your wetsuit! To give you better comfort, rash vests are a bit thinner than your actual wetsuit, with no sleeves-- no short nor long sleeves. The lining is either sponge-like to trap the water in or perfectly smooth like aluminium so as to stick tightly to your body. However, if this is still not enough, opt for a drysuit!
Fancy diving without making bubbles? It is indeed possible! The rebreather or Closed-circuit Rebreather (CCR) will allow you to recycle your air, and, basically, rebreathe it. It allows for greater underwater autonomy and a smarter and more optimized decompression management. It's a bit like a machine that produces the perfect Nitrox mix whatever your depth! This (expensive) piece of equipment is a must-have for marine biologists, underwater photographers and/or videographers, and for those who are really keen on deep or cave diving. The ultimate reason is that since the bubbles usually scare them away, the CCR enables you to get much closer to marine life!
Let’s talk technical. The rebreather passes your exhale through a tube filled with 'lime', which filters out carbon dioxide. Next, a tiny bit of pure oxygen and air are added to the mix before being reinjected into the breathing tube and repeat! It is called a loop since the process is neverending. And the best part? No bubbles!
A cylinder or a sealed steel cramped light-tight room that can hold one or more people and in which the pressure may be increased above ambient pressure—up to 2.5 bars and, in certain cases, more. It is mainly used to treat divers suffering decompression sickness. In addition to being placed in this pressurized environment, patients receive oxygen through a rebreather. This treatment greatly reduces the after-effects of decompression sickness by allowing the tiny nitrogen bubbles to re-dissolve and leave the patient’s body by air ways.
One or several recompression sessions are extremely expensive, so, please, let’s strive more for prevention and not intervention! To do this, make sure you're adequately covered for SCUBA diving and always follow the safety rules before, during, and after your dives: stay hydrated, no alcohol, come up slowly, no reversed profile, make a sufficiently long SI, etc.
Recreational/fun diving vs Tec diving
Recreational or fun diving's first aim is pleasure, and then comes fun and the discovery of a new environment. You usually dive, at the very most, 40 m deep and do not have any decompression stops to do-- only a small, not mandatory but highly recommended, safety stop for 3 minutes at 5 m of depth. Fun diving is mostly done with one, single or sometimes, but never more than, two tanks on your back!
Technical diving, or Tec diving, is done usually deeper than 40 m and/or in environmentally specific conditions like the inside of a shipwreck or an underwater cave. The main goal here is to explore and push your limits. This type of diving requires lots of experience, rigorous training, special equipment, and most often the use of mixed gases like Nitrox or Trimix. There are no real limits—except the human body’s—as to how far you can go down; however, most training programs (TDI, IANTD, PADI TecRec, etc.) stop their courses at 100m, which is already pretty far down! Decompression stops in Tec diving are mandatory: the further down you go and the longer you stay a given depth, the more numerous and lengthy the deco stops will be! The amount of tanks you carry on you is directly related to your breathing rate and your dive plan. This can start at 2 tanks and go up to 10 if necessary! Don’t take it lightly. Always stay on the conservative side of things and thoroughly plan your dives and make sure you won't run out of gas before resurfacing.
This is very useful for drift diving, especially for passing through the atolls. It enables you to relax and observe the fish without damaging anything while waiting for your dive buddy if the current is too strong.
Did you love your pacifier when you were a kid? Well here’s something similar that enables you to breathe underwater! It’s a system that hooks up to your tank and that goes into your mouth to give you all the air you need for your underwater explorations.
Technically, it reduces strongly compressed air from your tank (200 bars at full) to an intermediate pressure (10-15 bars), then ambient pressure. Basically, the first step is to reach the level of your first stage, the part hooked up to your tank. Then, second step is at the level of your second stage, the part that is in your mouth. When you exhale, air goes out the mouthpiece and makes bubbles. It is for this last reason that we call the regulator an open-circuit—it sends the diver’s exhale back in the water. Simple, right? This is the masterwork of the legendary French naval officer and sea explorer, Jacques Cousteau, and Emile Gagnan, an engineer in the 1940’s. Their first model was commercialized under the famous name Aqua-Lung!
SCUBA is a word or term everyone uses freely and matter-of-factly as it points to one single activity: underwater diving! It is actually an acronym for Self Contained Underwater Breathing Apparatus. Now you know!
SMB or Surface Marker Buoy
Do not expect to take the plunge! Well ok, this is still a safety object that alerts that allows the diver to be spotted during the ascent or to report a problem to surface security by attaching a slate to it. This is absolutely mandatory during drift dives and Tec diving.
SSI stands for Scuba School International. In sheer volume, it's the world's second, after PADI, largest school of diving and courses and training standards are quite similar to PADI. ALL THEIR CERTIFICATIONS ARE ACCEPTED IN ANY DIVE CENTER AROUND THE WORLD.
Safety stop or deco stop
Aaaaaah the deco/safety stops! These are two little words that nevertheless raise many conversations. Generally speaking, the less one knows about SCUBA diving, the faster these two words come up in a conversation. Let’s take a small moment to clear the air once and for all.
- First, what’s a stop? In fact, it’s a pause you take during the ascent, so towards the end—in no circumstance should you perform safety stops during the descent. The pause could last anywhere from 1 to several tens of minutes and this at a specific depth. In Tec diving, the more one approaches the surface, the longer the stops. In recreational diving, the stop is invariably 3 minutes at 5 m.
- What is the purpose of a stop? The first goal is to leave the time for the nitrogen that dissolved in the body throughout the dive to accommodate the new reduced ambient pressure and thus reach our lungs and be exhaled. By performing this little stop, the nitrogen evacuates gently, progressively, and in a controlled way from your whole body!
- Are there different types of stops? Yes, my captain! And, it is exactly on this point that clarification is needed:
-> For recreational diving, the diver is usually shallower than 40 m and NEVER saturates or fills the body with nitrogen. Thus, safety stops are NOT MANDATORY but highly recommended. It is carried out at 5m from the surface for 3 minutes at the end of your dive. It adds a safety and conservative element to your dive profile and allows your body to gradually adapt to the reduced ambient pressure before surfacing. If you don’t do this, it’s not a big deal and has (most likely) no medical consequences. This stop, referred to as “safety”, is a good practice and also a great way to bring together the whole dive group before the end of the dive.
->For Tec diving—the abbreviation for “technical”—1 or more safety stops are MANDATORY! The deeper and longer you dive, the faster your body fills up or saturates with nitrogen! Therefore, during the ascent, you should perform one or several safety stops in order to allow the excess nitrogen to get used to the slowly and gradually reduced ambient pressure and thus leave your body via your lungs when you exhale. If you don’t perform these stops, called “decompression stops”, the excess of nitrogen—because your body is full of it—will not have the time to get used to the new ambient pressure and will aggregate until forming tiny bubbles; this is what we call decompression sickness! Decompression stops during technical diving, a.k.a. “saturation diving”, must imperatively be respected!
- So, to stop or not to stop? Like many sports activities, SCUBA diving has 2 levels: amateurs of simple and accessible pleasure and thrill-seekers who love to push their limits. The first case, recreational diving, is accessible to everyone and requires basic training. It allows the diver to get straight in the water rather quickly after a short briefing and having a direct, permanent, and vertical access to the surface… without mandatory stop(s). In the second case, technical diving, it requires a lot of prior recreational diving experience and several rigorous and demanding trainings. Good planning is essential and saturation is an integral part of Tec diving so stops are mandatory!
Well, now you know! So go use the term loud and proud!
The dive season is over. The winter holiday’s merrymaking has left you with some extra pounds. And, you want to keep your dive skills sharp and up-to-date. Problem? Nah! Dive clubs all around the world offer courses in swimming pools or shallow waters throughout the year to stay in shape and continue to dive smart. You'll practice basic skills and review theory so you won't lose your sensations and technique. By the time your vacation comes, you'll be fit and ready to dive! If you don't opt for that method, make sure you take a short scuba review during your next vacation. Basically before diving a site that is just within or slightly above your comfort zone, take a class or two to review the basics with an instructor. It's way safer for you, and also, for the rest of your group! Put aside your ego and be honest with yourself: if you are feeling rusty or it's been over a year since you last dived, don't be complacent! Take a 'refresher'!
Sea turtles are reptiles from the Chelonioidea family. They're present in all the world's oceans (except the Arctic). The Leatherback turtle is the largest measuring up to 2 m long, over 1 m wide, and weighing in at about 600 kg! The average size of other turtle species varies from 50 cm to 1.5 m in length, with an accordingly proportional width. Unfortunately all sea turtles are a threatened and vulnerable species. Locally, they are protected and subject to conservation plans, but the overall pollution of oceans, poaching, and accidental by-catch in global fisheries cause a serious threat to all the turtles.
The main species:
- The green turtle: round shape, the shell is most often clean and the head pretty much 'round' too; they can live on reefs (if the food resources are sufficient) but are also pelagic and can cover great distances.
- The hawksbill turtle: oval in shape with a slightly 'pointy' shell that is usually dirty and covered in crust-forming algae; the beak, or bill, is similar to a bird’s with a slight hooked shape; they are mainly found on reefs where they reside.
- The leatherback turtle: huge in size with a very distinct shell where we can see its 'hems' running lengthways.
Sharks, a.k.a. man-eaters, the-danger-from-below, blood thirsty monsters, and the list goes on and on. All those sweet and adorable nicknames come from the fact that we fear what we don't know! The selacian, or elasmobranch, fish is too often portrayed as the devil incarnate. Although it's a predator, it is a predator varying in species, most of them completely harmless to humans, that is a CRUCIAL link to the marine food chain and, unfortunately, on the brink of extinction. In fact, oceans without sharks are like the bush with lions: it's bound to rot, and disappear. Indeed, Hollywood productions are a thrill and a lot of ill-informed documentaries hit the sensationalist sweet spot in us all, but the reality is really far from glamorous: sharks NEVER attack divers, and if and when they do attack swimmers or surface-dwellers it's most often because they’ve mistaken you for something else. (Hey, without arms and hands, they only have their mouths to identify something!)
As you know, the topic can go on forever. We recommend two websites (among the hundreds!) to get your facts straight:
Shore diving vs Boat diving
Are you prone to seasickness? No worries! You can shore dive; a more accessible solution for beginners and those of you who are a little sensitive to the motion of the ocean! Boat diving will allow you to get to dive sites that are hundreds of meters or miles away form the coast or that are exposed to environmental conditions that are too strenuous to swim to. There are but a few regions in the world that benefit from world class shore diving (Lembeh in Sulawesi, Indonesia; Fakarava Atoll in French Polynesia; Bonaire, in the Caribbean, to name a few). Otherwise, boat diving is most often the only way to go. It's the very nature of diving!
Sidemount diving is considered by some as the future of diving. You wear your tanks on one side of your body, along your rib cage with the tank valves under your arm pits. This setting gives you better streamlining, a feeling of freedom of movement, and enables you to better sneak in between cracks and crevices in wrecks or caves. Sidemount diving is taught as a specialization. You can find it here:
There are hundreds of different models and brands of snorkels and you need to find the one suitable for you depending on your budget and activity, i.e. spearfishing, freediving, swimming with fins, recreational snorkeling, etc. A snorkel has different characteristics to chose from like inhaling and exhaling comfort, shape, solidity, color, and valve system. Take some advice from the pros: the simpler, the better! The more features and gadgets you have on it (wave breakers, double purge valves, etc.), the more likely it is to break and not even last the summer.
The winning trio of the summer: fins, mask and snorkel! Snorkeling is all about swimming leisurely on the surface to observe fish in clear water. You can duck dive and breathhold every now and again, but don't get too carried away because the longer and deeper you go, the riskier it gets. So either stay on the surface or get some basic training in freediving!
Whatever your astrological sign, your top speed, or even if you’re a super swimmer, the expression “to swim like a fish” is complete nonsense. Water will always be 800 times denser than air and therefore a human eminently remains a land animal. So what can you do for SCUBA diving then? You can streamline! Reduce drag, rubbing, efforts, and air consumption. Be as efficient as possible. Look beautiful. Avoid damage and blend in the best you can with your environment. You’re streamlining baby! Or swimming like a fish!
What you need:
- Neutral buoyancy
- Slow regular kicking
- A perfectly horizontal position
- Perfect weighting—not too light, not too heavy
- Arms out straight in front, immobile
Time spent between two dives that allows the nitrogen absorbed from your first dive to off-gas and in this way, prevents too rapid saturation for the second. The general recommendation is an hour wait. During this time, drink plenty of water, laze about in the shade, take a nap, and let’s go again! Absolutely no alcohol during the SI, not even a little beer!
Surface supplied breathing equipment
Tube or flexible pipe connected to the surface used by divers so that they can breathe without a tank.
TDI stands for Technical Diving International. It was created in 1994 by the world's top technical divers and is today, with 13,000 active instructors worldwide, the leader in Tec dive training. ALL THEIR CERTIFICATIONS ARE ACCEPTED IN ANY DIVE CENTER AROUND THE WORLD, providing they do Tec diving of course!
During a dive, you might see the water getting all blurry in front of you? No need for new spectacles, what you are witnessing is called a thermocline. Basically, it's the division between two masses of water of different temperatures (caused by sun-heated water near the surface, upwellings, currents, etc.). It can be a difference of only a half degree but can feel a hell-of-a-lot colder. Anyway, that's what makes the water blurry. You're welcome!
In the air, we have two gases: oxygen (O2) and Nitrogen (N2). O2 is vital to life on Earth, and so much so for us Humans, but N2 is what we call an inert gas and kind of useless to human beings! In the same way that we need water to sustain life, we don't eat the water bottle once we're finished with it. We only use the water bottle to 'hold' the water. Well, O2 and N2 share the same bond!
Nevertheless, O2 and N2 both have toxic or narcotic properties when put under pressure:
- For N2 it's called Nitrogen narcosis, or the rapture of the deep. It only occurs at depths of +30 m and the symptoms are a mix between exhilaration and anguish. Although, between 30 and 40 m it's really no big deal, your decision-making capacities will start to become impaired as you go down deeper.
- For O2 it's called Oxygen toxicity, or hyperoxia. When you dive on air, this condition starts setting in at + 60 m. Symptoms may include convulsions, vomiting and visual impairment. As you have probably understood, this O2 problem is quite serious and the consequences can be dire.
Now that you understand these issues, here's an interesting question to put forward: What do you do if you want to dive deeper than 60 m? The answer is quite logical. Add a third gas to the mix: helium! Now you have a 3-gas mix... hence the name, Trimix. Helium doesn't really have a narcotic effect until a couple hundred meters down, so it is here to act as a buffer for O2 and N2 so they don't go all toxic or narcotic on your brain and body. As an aside, try and listen to your dive buddy's voice whilst deep down. Mickey Mouse anyone?
Trimix training is the last part of Tec dive training. To get there, you first need to accumulate a fair bit of experience in technical and deep diving, using different Nitrox mixes or even train to dive on air at 55 m! The training is demanding and requires high levels of rigor and self-control. But once you're fully certified, the sky's the limit! Or a couple hudred meters under the big blue!
A plastic slate with a carbon graphite pencil attached—an improved No 2 in fact-- hanging on your wrist or from your jacket enables you to communicate with the other divers and teammate by writing underwater. This special pencil produces a thick black line—more readable underwater than a regular pencil although that works too!
Dive gear requires daily and regular upkeep. Salt water is corrosive and if you want your gear to last you have to thoroughly rinse off your equipment with fresh water AFTER EACH DIVE. Whether it’s the mask, snorkel, suit, regulator, camera, etc., give it a full rinse and let dry in the shade on a line, hanger, or solid surface in a well-ventilated area. NEVER leave it in the sun! Neoprene and other silicones will deteriorate!
'Maaaan, you should have come this morning, the vis' was like... 30 m dude!' Every single diver in the world has muttered this sentence at least once in his/her diving life, and yes, those who opted to stay shorebound that day are (slightly) disappointed, to say the least! The visibility is a very subjective notion that depends on the water’s turbidity, i.e. how loaded in suspended particles it is, the amount of light, where the currents are coming from, the tides, etc. This affect how vivid the colors are, how close you need to stay to your buddy, and, finally, how much fish you're going to see. Less than 5 m is considered very bad, 15-20 m is the average for good, and +30 m is like, ahhhh, being in a swimming pool!
Intended for warm waters, the wetsuit is THE must-garment for SCUBA diving. It is made of several layers for your utmost comfort and thermal insulation. A tiny layer of water penetrates your suit and reheats through your own body heat. This thin layer slowly and steadily is renewed for the duration of your dive, hence the importance of having a suit really snug to your body. The layers range from 2.5-7mm and the suit comes in many lengths, but the favorite that really brings the smile to every diver’s lips is the shorty because it implies +25°C waters!