Scuba Diving Terminology: 35 Phrases You Need To Know

When you begin your journey as a recreational scuba diver, you are likely to hear some words and phrases you do not know, and you might think the divers are speaking another language. Many words are scuba-specific, and there is a lot of scuba diving terminology that is useful to know if you want to become a scuba diver. We have made this cheat sheet for when you are unsure what the heck these scuba divers are talking about! Ready to get dive-lingual? Here is the scuba diving terminology you need to know.


When it comes to scuba diving terminology, knowing what your diving gear is called and how other divers may refer to each piece of kit is essential. Here are the top diving equipment phrases to learn:

1. BCD/BC/Jacket: You will get to know the buoyancy control device (BCD/BC/jacket) quite well during your Open Water Diver program. It is used to help you control and maintain good buoyancy while diving. You can add air into it, and release air from it to stay in the perfect position in the water. 

2.Wing: A winged BCD is a type of jacket that only inflates at the back, rather than all around your body. These are most commonly used in technical diving.

3.Regs: Short for regulators, many divers shorten the word in diving conversations. The regulators are the set of hoses that attach your air tank to your BCD and your mouth for breathing.

4.Octopus/occy/alternate: The octopus is the alternate air source, after your main regulator that you keep in your mouth. You will always have a spare one, which is used in a sharing air situation.

5.First stage: This is the part of the regulators that connects to the tank. Depending on where you are in the world, you will use either a ‘DIN’ or a ‘yolk’ style first stage.

6.Inflator hose: This is usually located on the shoulder of the BCD and is connected to the tank. It has buttons which allow you to inflate or deflate the BCD.

7.Pressure gauge: A gauge to check how much air you have left in the tank. The answer is usually shown in PSI or BAR measurements, depending on where in the world you are diving.

8.Fins: NOT flippers! A common mistake with beginners, experienced divers will always use the word ‘fins’. If you do not know, diving fins are worn on your feet to help you move through the water easily.

Want to learn how to fin efficiently? Read this: From Novice to Pro: The 6 Best Finning Techniques for Divers

9.Mask: NOT goggles. Another common mistake, a diving mask differs from swimming goggles in that it also covers your nose.

10.Bottle/tank: The diving tank is attached to the BCD and is how you carry air along with you for your dive. The tank is sometimes referred to as a bottle. Tanks are usually made from either aluminium or steel.

11.Pony bottle: A pony bottle is a small tank of air that can be carried by the diver as an emergency supply. You will not see this so often in recreational diving, but pony bottles are sometimes used when deep diving or at remote destinations with strong currents.

12.O-ring: An O-ring is a small rubble circle that is used to make a seal in between parts. The connection part at the top of the tank will often have an O-ring, as well as parts of your regulators. You will hear this scuba diving terminology a lot on dive trips when people are doing multiple dives and need dive spares.

Want to dive like a pro? Here is: Scuba Diving Skills: Monthly Goals to Become a Better Diver

13.SMB/Sausage:surface marker buoy (SMB) is an inflatable tube that signals to boats and other divers that you are below the surface. This can be inflated by air at depth via the regulator.

14.Rashy: Short for ‘rash vest’ which is used for many water sports to protect the torso from the sun, or make a wetsuit feel more comfortable.

15.Logbook: A book or online app such as MySSI where you keep track of your dives. You will include information about how deep the dive was, how long the dive was for (bottom time), as well as what marine life you saw.

16.Nitrox: Nitrox refers to when the gas in the tank is mixed differently to standard air (21% oxygen and 79% nitrogen). Nitrox has a slightly higher percentage of oxygen, which means divers can have a longer bottom time without needing to shallow up. You can become a nitrox diver by completing an enriched air nitrox certification. These certifications are very popular and allow divers to get the most out of every dive.

Diving procedures and safety

Your safety is paramount, and you will learn all about how to stay safe in the water during your scuba diving courses. To get you started, here is the scuba diving terminology you are likely to need:

17.Getting bent/DCS: DCS (decompression sickness) is a medical condition that might occur from surfacing too quickly or from staying too deep for too long. It is sometimes referred to as ‘getting bent’ because it can cause pain in the body’s joints and cause the diver to bend or hunch over in pain.

RELATED: The 6 Best Ways to Prevent Decompression Sickness

18.Bottom time: This is how long a diver will stay underwater. Knowing your bottom time can help you calculate how long or how deep your next dive should be.

19.Deco: You should not experience deco dives in most recreational diving. A deco dive is where the diver has gone beyond no-decompression limits, so they must make a longer/extra safety stop on their way to the surface because they stayed too deep for too long. In deep technical diving, this is planned for, but it is avoided in recreational diving.

20.Off-gassing: When we dive our bodies take on nitrogen. Nitrogen bubbles can form in the body’s tissues and cause DCS if our body does not ‘off-gas’ the extra nitrogen properly (due to a fast ascent or pushing diving limits).

21.Surface interval: We make a surface interval in between dives to give our bodies time to off-gas before the next dive. You will hear this scuba diving terminology on any day when you are doing more than one dive.

READ MORE: Top 9 Things To Do On A Surface Interval

22.Safety stop: We make a safety stop at the end of a recreational dive to off-gas the nitrogen, while still being at a shallow depth (this speeds up the process compared to being on the surface). A standard safety stop is done for three minutes at a depth of around 5 meters (16 feet).

23.No-fly time: The standard guidelines for flying after diving are to wait 12 hours after diving once, and to wait 18 hours after two or more dives. Some divers like to wait 24 hours just to be sure. Flying after diving can be dangerous as it raises the risk of DCS.

Diving skills

There are lots of different dive skills to learn and practice, whether you are a beginner scuba diver, an Advanced Open Water diver, or an experienced tec diver. Here is the scuba diving terminology you will need as you hone your skills.

24.Backroll: This is a way to enter the water from a small boat when you are boat diving. The diver will roll backwards into the water. You will hear this scuba diving terminology used during your dive briefings – when your SSI Dive Guide tells you what to expect from your upcoming dive.

25.Giant stride: This is another way to enter the water and is more commonly used from a boat or ledge. The diver strides forward from a standing position. 

Want to know more? Here are: 3 ways scuba divers can enter the water from a boat

26.Buoyancy: This is your position in the water when you are diving. When you are ‘neutrally buoyant’ you are neither floating upwards (positively buoyant) nor sinking downwards (negatively buoyant). Your dive buoyancy can be controlled by using a mixture of your breath, the BCD, and a weight belt.

27.Hover: Hovering in the water is what you do when you are neutrally buoyant, and you are not kicking or sculling to move your body. Perhaps you are hovering to look at something interesting like the marine life in a rock crack or you are face to face with a beautiful manta ray.

28.Trim: This is your body’s position in the water and how streamlined you are. Having good trim means you will be horizontal in the water, with arms tucked in, and your hoses and gauges are also kept close to your body.

29.Dive buddy: Your dive buddy is who you will look out for during your dive, and who will look out for you. You should always be close to your buddy and check that they are okay regularly. One of the best things about scuba diving is the dive buddies and lifelong friends you make around the world. Check out our new Facebook community Underwater Explorers Worldwide to get inspired by our community of inclusive, passionate divers.

LEARN MORE: How to be the best dive buddy you can be

30.Equalize: When we dive, the pressure of going deeper will squeeze air spaces in the body. We have airspaces in the ears and sinuses, so a diver will usually hold their nose and blow to equalize the pressure. You should also add a little air from your nose to the mask if it starts to squeeze onto your face upon descent - this is also called equalizing. You learn how to equalize when you start scuba diving and it is an essential skill you will always need as a diver.

Extra scuba diving terminology

Okay, so you have mastered the essential scuba diving terminology, but there is always more to learn! Here are some bonus scuba diving phrases to help you blend in with more experienced divers and share your diving experiences:

31.Viz: The visibility of the water – or how far you can see ahead of you underwater and how clear the water is.

32.Narc’d/gas narcosis/nitrogen narcosis: This is a strange experience some divers have when they dive deep, usually past 35 meters (115 feet). The diver might feel sensations similar to being drunk. The symptoms usually go away simply by ascending a little bit.

33.Bait ball:bait ball is a large school of fish that swarm together to protect themselves against predators. It is an incredible phenomenon to witness and attracts large pelagic marine life such as whales, sharks, sea lions and dolphins. You can go diving with bait balls during South Africa’s sardine run, at Magdalena Bay in Baja California, and at Moalboal in the Philippines.

34.Thermocline: A thermocline refers to when the temperature of the water suddenly drops. Some deep dive spots have dramatic thermoclines where the water suddenly becomes very cold!

35.Liveaboard: A trip that divers can go on, where they live on the boat for a few days and make multiple dives at various dive sites. Liveaboard diving is very popular and allows divers to reach some of the world’s best (and most remote) dive destinations, like the Socorro Islands, the Galapagos Islands and the beautiful islands that diving in Palau is famous for.

Now you know your scuba diving terminology, we hope you are inspired to start diving!

Ready to begin? Then check out the different ways you can learn to scuba dive with SSI: