Are you looking for scuba diving terms and abbreviations or don’t know what your dive buddy is talking about?
Then you have come to the right place!
The Social Diving glossary explains the most common and important scuba diving terms and will help you find your way around the underwater world.
Scuba Gear Glossary
ABC Set – The essential scuba and snorkeling gear every diver needs, consisting of a scuba mask, snorkel, and scuba fins.
Bailout Bottle: A small tank carried as a backup air supply, particularly in technical diving.
Ballast: Weights used to help divers achieve neutral buoyancy.
BCD – Buoyancy Control Device – Also called a jacket or vest and helps us stay buoyant underwater by inflating and deflating it with air from our scuba tank.
Suggested Reading:
The best BCDs for scuba diving in 2025
Booties / Dive Boots – Neoprene footwear worn with open-heel fins. Also called dive boots.
Buoy: A floating device used to mark a specific spot on the water’s surface.
CCR (Closed-Circuit Rebreather): A type of rebreather where no exhaled air is released into the water.
Dive Computer – Device used by scuba divers to monitor bottom time, depth, and non-decompression limits while diving. Calculates nitrogen load in real-time and displays decompression stops and other info. Available in wristwatch, console, and air-integrated styles.
Suggested Reading:
The best dive computers in 2025
Dive watch – Watch that fulfills ISO 2645 standards and is waterproof and pressure-resistant to at least 100m/330ft. Used to be an essential part of the scuba gear, but mostly serves aesthetic purposes nowadays.
Suggested Reading:
Dive Table: A chart that provides guidelines for dive depth and duration to prevent decompression sickness.
DPV (Diver Propulsion Vehicle): A handheld device that propels divers through the water. Also called an underwater scooter.
Exposure Suit: A garment like a wetsuit or drysuit worn to protect against the cold.
First Stage Regulator: Connects directly to the tank valve and reduces the high-pressure air to an intermediate pressure.
Hood: A neoprene head cover used for thermal protection.
Mask: Also scuba mask, diving mask, or snorkel mask. A piece of equipment that covers the eyes and nose, allowing divers to see underwater.
Octopus – Our second regulator. Reserved for emergencies and dive buddy support.
Open-Circuit: Standard scuba system where exhaled air is released into the water.
Primary Light: The main dive light, typically brighter and more durable than a backup light.
Rebreather: A device that recirculates air, removing carbon dioxide and adding oxygen.
Reef Hook: A device used by divers to anchor themselves in strong currents while observing a reef.
RNT (Residual Nitrogen Time): The amount of nitrogen absorbed in the body from a previous dive.
Scuba Tank: A cylinder containing compressed breathing gas.
Sidemount: A configuration where scuba tanks are attached to the sides of the diver, rather than the back.
Suggested Reading:
Guide to Sidemount Diving 2025
SMB (Surface Marker Buoy): An inflatable buoy deployed by the diver to signal their position to boats on the surface.
Snorkel: A breathing tube used while swimming at the surface.
Suggested Reading:
Split Fins: Fins with a split down the middle, intended to reduce drag and make finning easier.
Stage Bottle: An extra tank with specialized gas mixtures for decompression or emergencies.
Wetsuit: A neoprene suit that provides thermal protection by trapping water close to the body.
Suggested Reading:
Wing: A type of BCD that inflates behind the diver, allowing for better streamlining.
Scuba Diving Glossary
ADI: Association of Diving Instructors, a scuba certification organization.
Air Consumption Rate: The rate at which a diver uses air from their tank, often measured in bar/minute.
Alternate Air Source – A backup regulator for sharing air with a buddy in case of an emergency.
Altitude diving – Diving at altitudes and elevations greater than 300m / 1,000ft requires special altitude diving procedures and techniques.
Suggested Reading:
Ultimate altitude diving guide
Apnea: Breath-holding while diving; commonly referred to as freediving.
Arterial gas embolism (AGE) – Decompression illness caused by trapped air expanding in our lungs and causing ruptures and barotrauma.
Ascent Rate – The speed at which a diver rises to the surface.
Atmosphere (ATM) – A measure of pressure, usually in relation to water depth.
Backroll – An entry technique for getting into the water from a boat with scuba gear on. Cover your mask and regulator with your hand while sitting on the side of the boat before falling backward into the water, tank first.
Bottom Time – The total time spent underwater during a dive.
Buddy Check: A safety check is performed with a diving partner to ensure all equipment is working properly.
Suggested Reading:
Console: The unit containing a diver’s submersible pressure gauge, compass, and often a dive computer.
Dive buddy – Your underwater partner during a dive. One of the rules of scuba diving is that we never dive alone. Therefore, we form buddy teams with our dive buddies, do a buddy check, and help each other in case of an emergency underwater.
The Bends – A different term for decompression sickness after nitrogen bubbles have formed in tissues and joints of a diver. This can happen after ascending to the surface too quickly or when failing to take mandatory decompression stops.
Buddy Check – Before every dive, our dive buddy and we check each other’s scuba gear setup and make sure we are ready for diving.
Suggested Reading:
Cave Diving: Diving in underwater caves; specialized training is required. Read our cave diving guide!
Cavern Diving: A type of diving in overhead environments that are still partially open to daylight; less restrictive than cave diving.
C-Card/Certification Card – The card you receive upon completing a scuba diving course or specialty. Usually required by dive centers and operators before the first dive to prove sufficient certification. May be plastic, bio-degradable, or electronic.
Ceiling: The shallowest depth a diver can ascend to safely during decompression.
Check dive – Some dive bases and operators may require a check dive from new divers or those, who haven’t dived with them before. During the dive, an instructor or divemaster checks basic scuba skills like mask clearing, regulator retrieval, and octopus sharing to determine whether the diver is fit to dive.
Coral Bleaching: The loss of color in coral due to environmental stress, such as elevated water temperatures.
DAN: Divers Alert Network, an organization that provides emergency medical advice and assistance for divers.
Decompression: The process of slowly ascending to allow nitrogen to safely off-gas from the body.
Decompression illness (DCI) – Overall term for injuries related to the reduction of the ambient pressure around us.
It includes decompression sickness and arterial gas embolism. Read more here.
Decompression sickness (DCS) – Decompression illness is caused by dissolved gas bubbles entering body tissues causing damage and pain.
DIN valve – Type of valve on scuba tanks and scuba regulators. In contrast to Yoke, it is threaded and the o-ring is placed on the first stage of the regulator.
Suggested Reading:
Dive Flag: A flag used to indicate divers are in the water; usually red with a white diagonal stripe.
Dive Master: A certified individual who leads dives but is not a full instructor.
Dive Profile: A graphical representation of a diver’s depth and time during a dive.
Drift diving – A special version of current diving in which the start and end point of the dive are different. We jump in the water and swim with the current while the captain of the boat follows us.
EANx: Enriched Air Nitrox, a breathing gas with a higher oxygen content than regular air. Commonly referred to as Nitrox
Equalization: The process of balancing ear and sinus pressure while descending and ascending. Necessary to take care of your ears while diving.
Finning: The action of using fins to propel through the water.
Flutter Kick: A common scuba fin kicking technique involving straight-leg kicks.
Freeflow: Uncontrolled flow of air from a regulator, often due to cold or malfunction.
Gas Mix: The combination of gases in a scuba tank; can be air, nitrox, trimix, etc.
Giant Stride: A method of entering the water by taking a large step off a boat or pier.
Goodman Handle: A type of handle commonly used to hold a dive light.
Halocline: A layer in the water where saltwater and freshwater meet, often causing visual distortion.
Hand signals – Underwater, we use simple sign language with our hands to communicate with each other. Make sure to review these signals with your dive buddy during the buddy check.
Hogarthian Configuration: A streamlined equipment setup favored by some cave and wreck divers.
Hyperbaric Chamber: Another term for a recompression chamber.
Hypothermia – A medical condition experienced when the body loses heat too fast, causing dangerously low body temperature. Often experienced when diving in cold water and with insufficient thermal insulation.
Hyperthermia – Medical condition experienced when the body overheats, causing dangerously high body temperature. Often experienced by divers wearing their wetsuits in the heat without sufficient hydration or cooling.
IMCA: International Marine Contractors Association, responsible for best practices in commercial and professional diving.
ISO (International Organization for Standardization): Provides global standards, including those for scuba diving equipment.
J-Valve: An older type of valve on a scuba tank that automatically provides a reserve of air.
Knot: A unit of speed, commonly used in nautical settings, including diving.
Latent Hypoxia: A form of hypoxia that may not show symptoms until the diver ascends.
Line Arrow: A marker placed on a guideline in cave or wreck diving.
Liveaboard – Also called a diving safari. Divers spend the entire dive trip on a boat where they eat, sleep, and dive from without going on land. Most divers say this is the best way of traveling as a scuba diver.
Suggested Reading:
Manifold: A device connecting two tanks, allowing the diver to breathe from both simultaneously.
Marine Reserve: An area where fishing and other potentially damaging activities are restricted to protect marine life.
Multilevel Dive: A dive that involves descending to different depths.
Nautical Mile: A unit of distance used at sea, equal to 1,852 meters or 1.1508 miles.
Nitrogen Narcosis: A condition that affects divers at depths usually greater than 100 feet/30m, causing confusion and poor decision-making.
Nitrox – Also called EANx (enriched air nitrox) where x indicates the oxygen content in percentage. Special breathing gas used to increase non-decompression limits during diving. Short for “Nitrox” & “Oxygen”.
We have a guide to Nitrox Diving, too!
NOAA: National Oceanic and Atmospheric Administration, responsible for various marine guidelines including dive tables.
Non-Decompression Limit (NDL) – Indicates the available bottom time during a dive without a required decompression stop. Our dive computer displays the current NDL in real-time.
Open Water: A certification level for basic scuba diving, as well as a term for a non-confined water environment.
Overhead Environment: Any environment where a direct vertical ascent is not possible, such as caves or wrecks.
OWD: Open Water Diver, the basic certification level for recreational scuba diving.
PADI: Professional Association of Diving Instructors, a major scuba certification organization.
PSI: Pounds per Square Inch, a unit of pressure.
Purge Button: A button on a scuba regulator that allows manual release of air.
Quarry Diving: Diving in an old, water-filled quarry; often used for training.
Recompression Chamber: A chamber used to treat divers suffering from decompression illness.
Reef hook – Device used to hook into a reef during a dive in strong currents. Often used at diving destinations like the Maldives to observe sharks without having to do a drift dive.
Safety Stop: A 3-5 minute pause at 15-20 feet / 5m during ascent to allow nitrogen to off-gas.
SSI: Scuba Schools International, another major scuba certification organization.
Silt Out: When visibility is reduced due to sediment being stirred up. A dreaded occurrence in cave diving and wreck diving.
Surface Interval – Time between two (repetitive) dives. The longer our surface interval, the larger our non-decompression limit (NDL) the next time.
Swim thru – Short underwater tunnel or opening that we swim through during a dive. Technically, it classifies as an overhead environment, but it’s mostly too short to be considered that.
Technical Diving: Advanced forms of scuba diving that exceed recreational limits, involving specialized equipment and training.
Thermocline: A layer in the water column where there is a rapid change in temperature.
Trim: The diver’s orientation in the water, ideally horizontal for streamlining and efficient swimming.
Trimix: A gas mix containing oxygen, nitrogen, and helium, used in deep and technical diving.
Underwater Navigation: The skill of finding one’s way while submerged.
Valve: A device on a tank that controls the flow of air.
Viz: Short for visibility; refers to how clear the water is during a dive.
Wall Dive: A dive along a vertical underwater cliff.
Xenophyophore: A type of large, single-celled organism sometimes encountered in deep-sea diving.
Yaw: The side-to-side movement or turning motion of a diver or submersible.
Yoke – Type of valve on scuba tanks and scuba regulators. In contrast to DIN, it features a clamp-type mount on the regulator that is placed on the tank valve sealed by the main O-ring.
Suggested Reading: