Scuba Diving Acronyms and Terms

ABCDE stands for Air, BCD, Computer, Dive Equipment, and Enter the water. It is 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 are designed to be easy to use, with prompts and pictures. If you dive, you should be trained to use one and know where it is kept.

Arterial Gas Embolism usually results from holding your breath during ascent. As air expands, lung tissue can rupture and allow bubbles to pass into arteries. This can cause stroke-like symptoms or loss of consciousness. It is 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 is convenient, but it is another potential failure point, so know how to dive without it.

Advanced Open Water includes dives like deep and navigation. It is often marketed as a way to gain confidence and dive to 100 feet. Despite the name, it does not make you an “advanced” diver. It introduces a broader set of conditions, and 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 job with different designs. Mastering your BCD is key to safe and enjoyable diving, and it is one of the first major skill hurdles new divers face.

Instead of a padded jacket, BP/W setups use a metal plate, harness, and a donut or horseshoe-shaped wing. They are 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 is meant to ensure that both you and your buddy are ready to dive. The aim is to avoid 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 is not just polite; it can save your dive or your life.

A Controlled Emergency Swimming Ascent is used when a diver has no access to a gas source at depth and must swim to the surface. Ascend slowly, exhale continuously to prevent lung overexpansion, and maintain control without panicking. It is a last-resort technique taught in Open Water and signals a failure in gas planning or buddy awareness.

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 will need it urgently.

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

Also called a tank or bottle. Cylinders come in various sizes, materials such as steel or aluminum, and working pressures. Understanding what you are 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 such as nitrogen is not properly off-gassed during ascent. This includes both Decompression Sickness, where bubbles form in tissue, and Arterial Gas Embolism, where bubbles enter the bloodstream. 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 such as rash or joint pain to severe such as paralysis or 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 decompression obligation increases your risk for DCI. Always monitor your dive computer and dive your plan.

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

DIR emerged from high-risk cave diving and promotes consistency, control, and team cohesion. It focuses on standardized gear setup, streamlined profiles, redundancy, and clear communication. DIR is not a brand or agency but a philosophy, and it underpins GUE training while influencing 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 is a critical skill.

One atmosphere of pressure is reached at 33 feet of salt water, FSW, or about 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 is usually negligible. You will 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. The course has two levels: Recreational qualifies for recreational GUE courses, and Technical is required for GUE tech or cave tracks.

GUE-EDGE stands for Goal, Unified team, Equipment, Exposure, Decompression strategy, Gas planning, and Environment. It is a verbal run-through before every dive to align the team. Even if you are not GUE-trained, adopting 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-gas situation. The long hose is typically 5 to 7 feet and is routed under the arm and around the neck. It is standard in cave, technical, and DIR diving, and it is increasingly popular in recreational team-focused setups.

Your Local Dive Shop is often the first place you will interact with the dive community. Shops may offer training, gear service, rentals, and group trips. Supportive dive shops are a great resource, but not all are 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 are used in search and recovery, technical diving, and training scenarios. Recreational divers sometimes use them incorrectly. Learn proper deployment and rigging if you are going to use one.

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

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 pay attention.

Nitrox, usually 32 percent or 36 percent oxygen, extends your No-Decompression Limits by reducing nitrogen exposure. It does not let you go deeper; it has a shallower MOD. You will need a specialty certification to use it, and it is widely available.

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. Whatever you use, practice donating and retrieving it.

Open Water certifies you to dive to 60 feet, or 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 recognized certifying bodies with 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 often matters more than the agency.

Patent Foramen Ovale occurs in about 1 in 4 people and often goes undetected. In diving, it can allow nitrogen bubbles to bypass the lungs, raising DCS risk. Most divers with a PFO never have issues, but repeated DCS events may prompt testing or corrective procedures.

A pony bottle is a completely independent gas source with its own regulator for use if your primary supply fails. It is 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 you breathe from. It reduces tank pressure to ambient pressure. Most setups include a primary and an octo or backup. Regular maintenance is essential for safe performance.

A Rigid Inflatable Boat is a small craft with a rigid hull, typically fiberglass or aluminum, surrounded by inflatable tubes. RIBs are common for diving because they are stable, fast, and easy to maneuver in rough water. Space is limited, so secure gear carefully and keep hoses tidy to prevent snags.

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

Your SAC rate is measured in PSI per minute or BAR per minute and lets you estimate how long your gas will last at depth. It is less useful than RMV but is easier to calculate and track. Many divers monitor SAC trends to measure improvement.

Self-contained Underwater Breathing Apparatus started as an acronym but is now used as a regular word. It refers to systems where a diver carries their own gas. Open-circuit scuba vents exhaled gas into the water, while rebreathers recycle part of that gas for efficiency.

Surface Consumption Rate is functionally equivalent to RMV. The term is most commonly used by GUE-trained divers. In practice, RMV has wider adoption in planning tools and reference materials.

A silt-out happens when you stir up fine sediment, often from poor finning or bottom contact. It is dangerous in confined spaces and annoying everywhere else. Good trim and propulsion techniques such as frog kicks help prevent it. Always carry a light in low-vis environments.

An SMB stays at the surface and improves visibility during drift dives or in areas with boat traffic. It can be attached to a line, reel, or spool. A dSMB is launched from depth during ascent. Every diver should know how to deploy and manage one.

SPGs can be analog with a needle or digital as part of an air-integrated computer. Always check the units, PSI or BAR. Analog SPGs often show a red warning zone between about 500 and 700 PSI, but not all do. Check function before every dive and never assume accuracy.

“Tank,” “cylinder,” and “bottle” are used interchangeably in diving. What matters is the pressure, volume, and gas mix inside. Aluminum tanks are common in tropical locations, while steel tanks are often used in cold water or technical setups. Match the tank to the dive and weighting.

Good trim reduces drag, improves buoyancy control, and prevents disturbing the environment. Many new divers are unintentionally feet-down or tilted. A flat, horizontal position improves safety and propulsion efficiency. It is 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 are easy to use and very common at recreational shops. They are not rated for the highest pressures and are more prone to impact damage than DIN. Learn both styles if you travel internationally.