Scuba Diving Acronyms and Terms

ABCDE stands for Air, BCD, Computer, Dive Equipment, and Enter the water. It’s taught by several agencies as a structured buddy check. The letters vary depending on where you trained, but the goal is the same: verify your gear before you get wet.

AEDs analyze a person’s heart rhythm and deliver a shock if needed. They’re designed to be easy to use, with prompts and pictures. If you dive, you should be trained to use one and know where it’s kept.

Arterial Gas Embolism usually results from holding your breath during ascent. As air expands, lung tissue can rupture, allowing bubbles to pass into arteries. This can cause stroke-like symptoms or loss of consciousness. It’s one of the most urgent emergencies in diving and demands immediate oxygen and evacuation.

Air Integration uses a transmitter or cable to show your tank pressure on your wrist computer. Some computers also calculate gas time remaining or let you see your buddy’s pressure. It’s convenient, but also another potential failure point so know how to dive without it.

Advanced Open Water includes dives like deep and navigation. It’s often marketed as a way to gain confidence and dive to 100 feet. Despite the name, it doesn’t make you an “advanced” diver — it just introduces you to a broader set of conditions. Skill comes with repetition.

BAR is used outside North America and is common on gauges and compressors worldwide. To convert: 200 BAR × 15 ≈ 3000 PSI or 3000 PSI ÷ 15 ≈ 200 BAR. Always check the units on SPGs and rental gear — mixing up BAR and PSI can lead to dangerous confusion.

The BCD holds your tank and lets you add or release air to stay neutrally buoyant. Jacket-style, back-inflate, and BP/W systems all do the same thing differently. Mastering your BCD is key to safe and enjoyable diving and one of the first big skill hurdles new divers face.

Instead of a padded jacket, BP/W setups use a metal plate, harness, and donut or horseshoe-shaped wing. They’re customizable, travel-friendly, and favored in technical and GUE-style diving. Once adjusted properly, they can be more stable and streamlined than traditional BCDs.

BWARF stands for BCD, Weights, Air, Releases, and Final OK. Like ABCDE, it’s meant to ensure that both you and your buddy are ready to dive, without skipping important steps in the rush to get underwater.

A buddy check is your last chance to catch gear issues before you enter the water. Whether you use BWARF, ABCDE, or your own routine, the goal is to verify air is on, weights are secure, and everything is working. It’s not just polite, it can save your dive or your life.

A CESA is performed when a diver has no access to a gas source at depth and must ascend while swimming to the surface. The diver must begin ascending slowly, exhale continuously to prevent lung overexpansion, and maintain control without panicking. It’s a last-resort emergency technique taught in Open Water training and a sign that something went horribly wrong in gas planning or buddy awareness and unlikely to actually be used in the real world.

CPR involves chest compressions and rescue breathing to keep oxygen moving through the body. Every diver should take a CPR course, ideally combined with first aid and emergency oxygen training. You may never need it, but if you do, you’ll need it badly.

Short for “certification card,” your C-card shows you’ve completed a course with an agency like PADI, SSI, or NAUI. You’ll need it to book dives, rent gear, or get air fills. Most agencies now offer digital versions, but it’s smart to carry a physical one too.

Also called a tank or bottle. Cylinders come in various sizes, materials (steel or aluminum), and pressures. Understanding what you're breathing, how much you have, and how to read your SPG is far more important than which name you use.

Decompression Illness happens when inert gas (like nitrogen) is not properly off-gassed during ascent. This includes both Decompression Sickness (bubbles in tissue) and Arterial Gas Embolism (bubbles in blood). DCI is rare, but possible even within limits. Know how to recognize it, and always dive with a plan.

Often called “the bends,” DCS occurs when nitrogen forms bubbles in tissues during or after ascent. Symptoms can range from mild (rash, joint pain) to severe (paralysis, collapse). Oxygen and rapid medical attention are critical. Prevention starts with controlled ascents and awareness of your limits.

Technical divers plan for decompression; recreational divers try to avoid it. If your dive goes beyond No-Decompression Limits, you are no longer free to surface at will. Exiting without completing your deco obligation puts you at high risk for DCI. Always monitor your dive computer and dive your plan.

DIN valves are threaded and form a stronger seal than yoke systems. They’re standard in technical diving and widely used outside North America. They reduce the chance of a regulator getting knocked loose, especially at higher pressures or with multiple tanks.

DIR emerged from high-risk cave diving environments and promotes consistency, control, and team cohesion. It focuses on standardized gear setup, team procedures and shared responsibility, streamlining, redundancy, and communication. DIR is not a brand or agency but a philosophy. It’s the backbone of GUE training and has influenced many divers beyond that system.

Unlike a basic SMB, a dSMB is inflated underwater and sent to the surface during ascent or safety stops. It tells boats where you are and signals your position before you surface. Learn to launch it from depth without losing control or entangling yourself, it's a critical skill.

1 atmosphere of pressure is reached at 33 feet of salt water (FSW) or 34 feet of fresh water (FFW). Some dive computers allow you to toggle between the two. It makes a small difference, but at recreational depths it’s usually negligible. You’ll see these units used in tables, gauges, and training materials.

Fundies is short for “GUE Fundamentals.” The course teaches precise buoyancy, horizontal trim, propulsion techniques, and situational awareness. It emphasizes team skills, gas planning, and efficient communication. It’s not just for technical divers, many recreational divers take it to develop solid baseline skills. The course has two levels: Recreational qualifies for recreational GUE courses, and Technical is required for GUE tech or cave courses. Even seasoned divers often find it sharpens their control and habits.

GUE-EDGE stands for Goal, Unified team, Equipment, Exposure, Decompression strategy, Gas planning, and Environment. It’s a verbal run-through before every dive, ensuring the entire team is aligned. Even if you’re not GUE-trained, adopting the habit of a structured dive briefing improves safety and clarity.

Also called “long hose routing,” this setup allows the diver to donate their primary regulator in an out-of-air situation. The long hose is typically 5 to 7 feet and routed under the arm and around the neck. It’s standard in cave, tech, and DIR diving — and increasingly popular in recreational setups focused on team diving.

Your Local Dive Shop is often the first place you’ll interact with the dive community. They may offer training, gear service, rentals, and group trips. Supportive dive shops can be a great resource, but not all are created equal. Ask questions, compare prices, and find one that fits your needs and values.

Lift bags trap air underwater and use it to provide upward force. They’re used in search and recovery, technical diving, or training scenarios. You’ll sometimes see recreational divers use them incorrectly. Always learn proper deployment and rigging if you’re going to use one.

Minimum Gas Reserve is based on gas planning and ensures that if something goes wrong, you and your buddy can safely ascend. It accounts for depth, consumption rate, and time. Even recreational divers should understand the concept. Surfacing with “just enough” is not a plan, it’s a risk.

Maximum Operating Depth depends on the oxygen content of your gas and the maximum allowable partial pressure of oxygen (usually 1.4 ATA for diving). Breathing gas past its MOD increases the risk of oxygen toxicity. Know how to calculate MOD, especially when diving Nitrox.

If you stay within your No Decompression Limit, you can ascend directly (with a safety stop). Exceeding it means you must stop at certain depths to off-gas safely. NDLs vary with depth, gas mix, and dive profile. Your dive computer tracks this in real time so always pay attention to it.

Nitrox, usually 32% or 36% oxygen, extends your No-Decompression Limits (NDLs) by reducing nitrogen exposure. It does not let you go deeper; in fact, it has a shallower MOD. You'll need a specialty certification to use it, but it’s widely available and commonly used on recreational dives.

The octo is your alternate air source, used if your buddy runs out of gas. Standard recreational setups position it on a yellow hose in an easy-to-find location. In long-hose configurations, your primary is donated and the octo is for you. Whichever you use, practice donating it regularly.

Open Water certifies you to dive to 60 feet (18 meters) with a buddy. It covers gear basics, dive physics, safety procedures, and underwater skills. The quality of instruction matters a lot so choose your instructor as carefully as your agency.

These are all recognized certifying bodies, each with slightly different teaching styles and standards. PADI has global reach and a modular structure. SSI emphasizes digital materials and flexibility. SDI focuses on real-world diving and online coursework. NAUI is known for academic depth and instructor autonomy. Your instructor matters more than the agency as a great teacher makes any course worthwhile.

Patent Foramen Ovale ooccur in about 1 in 4 people and often go undetected. In diving, they can let nitrogen bubbles bypass the lungs, raising DCS risk. Most divers with a PFO never have issues, but repeated DCS hits may prompt testing or corrective surgery.

A pony bottle is a completely independent gas source, with its own regulator, used in case of primary gas failure. It’s not the same as an octo, which shares your main gas supply. Ponies are common in solo, deep, or wreck diving. If you carry one, practice deploying it.

Most US-based divers will learn PSI by default. To convert quickly: 3000 PSI ÷ 15 ≈ 200 BAR or 200 BAR × 15 ≈ 3000 PSI. Always check your SPG, mixing up BAR and PSI can result in major misreads or dangerous dives.

A regulator has two main parts: the first stage (attached to the tank) and the second stage (the part you breathe from). It reduces tank pressure to ambient pressure. Most setups include a primary, an octo or backup. Regular maintenance is essential.

Respitory Minute Volume is more useful than SAC rate because it factors in tank size. It's typically used in technical dive planning, basic gas planning, and stage gas calculations. Knowing your RMV lets you plan more advanced dives with higher confidence in your reserves.

Your SAC rate is measured in PSI/min or BAR/min and lets you estimate how long your gas will last at depth. It’s less useful than RMV but much easier to calculate and track.

Self Contained Underwater Breathing Apparatus was originally an acronym but is now used as a regular word. It refers to any system where a diver carries their own gas. Open-circuit scuba, what most recreational divers use, vents exhaled gas into the water. Rebreathers, used by some advanced divers, recycle that gas.

Surface Consumption Rate is functionally equivalent to RMV. The term is typically only used by GUE trained divers

A silt-out happens when you stir up fine sediment, often with poor finning or contact with the bottom. It’s dangerous in confined spaces and annoying everywhere else. Learn good trim and propulsion, frog kicks and awareness prevent it. Always carry a light in low-vis environments.

An SMB stays at the surface and is used for visibility, especially during drift dives or in boat-heavy areas. It can be attached to a line, reel, or spool. A dSMB is a variation launched from depth. Every diver should know how to deploy and use one.

SPGs can be analog (needle gauge) or digital (part of an air-integrated computer). Always check the units (PSI or BAR). Analog SPGs often have a red warning zone between 500 and 700 PSI, but not all do. Check before every dive, and never assume it’s working.

“Tank,” “cylinder,” and “bottle” are used interchangeably in diving. What matters is understanding the pressure, volume, and gas mix it contains. Aluminum tanks are more common in tropical locations; steel tanks are often used in cold water or technical setups.

Good trim reduces drag, helps control buoyancy, and prevents disturbing the environment. Many new divers are unintentionally feet-down or tilted. A flat, horizontal position improves safety and makes propulsion more efficient. It’s one of the clearest indicators of a skilled diver.

Yoke regulators clamp over the tank valve and seal with pressure from an O-ring. They’re easy to use and very common at recreational shops. They’re not rated for extremely high pressures and are more prone to damage than DIN valves. Learn both styles if you travel internationally.