Scuba Diving Glossary

• Absolute pressure: The equivalent of atmospheric pressure plus gauge pressure calculated by using perfect vacuum as the 0 point.
• Acetal resin: Very strong, high performance polymer used to replace lightweight metal.
• Air: Gas mixture comprised of 21 percent oxygen, 78 percent nitrogen, and 1 percent other gases that when compressed becomes breathable air used for scuba diving.
• Air compressor: A piece of scuba diving equipment that compresses or pressurizes air.
• Air tank: Cylinder of compressed air used for scuba diving.
• Alternate air source: Secondary or backup regulator used in place of the primary regulator in emergency cases.
• Ambient light: Natural underwater sunlight.
• Ambient pressure: Surrounding pressure on land from the weight of the atmosphere. Underwater, ambient pressure is the pressure that occurs from the surrounding water.
• Analog device: Pressure gauge involving a needle moving around a dial used for dive tanks.
• Argon: Gas that makes up about one percent of air.
• Ascent/descent line: Surface line that controls a diver's rater of ascent and descent into the water.
• Atmospheric pressure: Pressure of the weight of the atmosphere.
• Artificial spit: Scuba mask defogging liquid.
• Ascent bottle: Extra cylinder of air used for decompression stops during deep diving.
• Axial flow scrubber: Scrubber canister used in re-breathers where exhaust enters one end and exits the other.
• Back gas: Breathing gas contained in cylinders carried on a diver's back.
• Bail-out bottle: Tank containing backup air to be used only in cases of emergency.
• Bar: Term used in measuring atmospheric pressure. One bar equals 15 lbs of atmospheric pressure per Basic cave training: Training that covers the basics of cave diving.
• The bends: Term used to denote decompression sickness.
• Bladder: Container of air inside of buoyancy compensator that balances buoyancy levels.
• Booties (scuba booties): Neoprene socks worn by scuba divers.
• Bottom time: Length of time a diver is underwater.
• Bottom timer: Depth timing device that automatically starts when the diver begins descending.
• Breathing loop: Part of a re-breathing system comprised of a mouthpiece, inhalation and exhalation bags, hoses, and canister.
• Buddy bottle: Independent bottle carried by a diver in the place of dive buddy in cases of emergency.
• Buoyancy: Upward force exerted on something in water.
• Buoyancy compensator: Inflatable vest worn by the diver to help control buoyancy.
• Buoyancy control device: Device that aids a diver in maintaining proper buoyancy.
• Burst disk: Copper disk designed to break when tank pressure is exceeded.
• Boots: Foot protection on land or in water, usually made of neoprene.
• Bypass valve: Manual valve that lets gas into the breathing loop of a re-breather.
• Cage: Acronym for "cerebral arterial gas embolism".
• Canister light: Large, long-burning light attached to a battery pack contained in a canister used for scuba diving.
• C-card: A diver's certification card.
• Caustic cocktail: Very dangerous mixture of water and hydroxide chemicals caused by water flooding the scrubber canister.
• Cave diving: Highly specialized diving requiring special training and equipment due to the fact that it involves an overhead environment preventing a diver from making a direct descent into the water.
• Certification dive: Open water dives that a diving trainee performs after completing their academics and pool work.
• Check-out dive: A dive that demonstrates diver possesses the necessary skills required for a dive.
• Check valve: Re-breather valve that ensures that gas or fluid only flows in one direction.
• Closed circuit scuba: Noiseless and bubble-less, a circuit allowing divers to re-breath exhaled air by removing the C02 and replacing it with 02.
• Compressed air: Air that is kept under a certain pressure in order to be used as a source of breathing air for scuba diving.
• Counter lung: The breathing bag component of the re-breather system.
• Cylinder: Scuba tank containing breathable gas.
• Deco: Short for decompression
• Decompression: Reducing ambient pressure resulting in reduced gas pressure within the body.
• Decompression sickness: Illness that occurs when ambient pressure is reduced and nitrogen leaves the body.
• Decompression stop: Also called a safety stop, a set time and depth of a diver to eliminate inert gasses in order to avoid decompression sickness.
• Deep diving: Refers to either recreational diving up to 60 feet, or technical diving up to 130 feet.
• Deep stops: Stopping to note physical symptoms after completing several deep dives in order to help stabilize gas tension for the ascent.
• Demand valve: Part of the diving regulator that delivers gas to the mouth.
• Depth gauge: Measures the depth of a diver.
• Dive computer: Electronic device that measures inert gas pressure levels, depth, time, ascent rates, warns diver about decompression stops, and more.
• Dedicated dive resort: A resort designated for recreational scuba diving.
• Dive skin: Full body suit made of a thin piece of material, usually Lycra, to protect the diver from scrapes and stings.
• Dive buddy: Underwater diving partner.
• Diving weights: Weights worn by diver to offset body buoyancy.
• Doubles: Two cylinders banded together for extended dives.
• Drift diving: Diving with the current, as opposed to anchor diving.
• Dry suit: water proof, water tight insulating garment to help keep the diver's body warm.
• Duel regulator systems: Two regulators attached to a single air supply as an extra safety precaution.
• Enriched air nitrox: Oxygen enriched breathing gas used instead of compressed air.
• Exhaust valve: One-way valve in the exhaust hose to keep gas flowing in the right direction.
• Exposure protection: Body suit worn by a diver to maintain body temperature and protect the body.
• Fins: Equipment worn on the feet to help propel the body through the water while kicking the legs.
• First stage regulator: Regulator attached to the scuba cylinder valve to stabilize tank pressure.
• Flow meter: Device that shows the flow rate.
• Flow restrictor: Restriction placed in a flow line, often used with low pressure hoses, to limit the volume of gas.
• Gaiters: Wraps used to squeeze airspace from the lower legs of a wet suit to help maintain proper buoyancy.
• Galvanic corrosion: Corrosion of two or more metals in contact with each other.
• Galvanized: Metal preservation using rust resistant zinc coating on steel.
• Gas analysis: Method to determine fractions of gas contained in a breathing mixture.
• Gauge reader: A bifocal lens that helps a diver read a gauge.
• Granny line: Also called a 'Jerry line'; a line running from the hang bar to the anchor line.
• Gas saturation: Level of dissolved gas in body tissue reaches its maximum.
• Halocline: Change in salt content in water not apparent to divers unless it creates buoyancy changes.
• Hang tank: Extra tank containing deco mix used during the decompression stop.
• Harness: Used to secure a back-plate to a diver.
• Heliox: Combination helium and oxygen used for very deep diving.
• Helium: A light gas used for very deep diving.
• High pressure cylinder: Steel cylinders used at pressures of 3,500 csi.
• Hogarthian: Named after Florida cave diver William Hogarth Main, a configuration based on lowering equipment to a minimum configuration to maximize gas efficiency.
• Hookah: Surface-supplied breathing apparatus consisting of a cylinder and a long hose, used for shallow diving.
• HP hose: High pressure hose attached to a first stage regulator and running to the air pressure gauge.
• Hyperbaric chamber: Air tight chamber used for treating decompression sickness.
• Independent doubles: Double cylinder diving without a manifold.
• Inflator valve: Buoyancy compensator valve to which a second stage low pressure hose is attached.
• J-valve: An older kind of cylinder valve that released reserves gas by way of a spring loaded part.
• Jasper reel: Named after Florida diver Woody Jasper, a reel with a handle on the side instead of on top.
• Jon line: Short line divers attach to anchor line used for decompression diving.
• K valve: On/off cylinder valve.
• Kit: British for diving equipment.
• Lay line: In cave diving, the first line used in an unexplored cave site.
• Lift bag: Bag divers use to lift underwater objects.
• Lift capacity: Amount of buoyancy given by a buoyancy compensator.
• Manifold: Piece of scuba equipment used for double cylinder systems.
• Mask: Glass window in diving helmet allowing diver to see clearly underwater.
• Mask squeeze: What occurs when a diver fails to equalize his or her mask before a rapid descent.
• Mixed gas: Non-air mixture, or gas mixed with nitrogen.
• MOD: Acronym for "maximum operating depth".
• Mooring Buoy: Permanent marker for tying a dive boat to, often used to mark common dive areas.
• Multilevel diving: Spending time in varying depths in a single dive.
• Mushroom valve: Second stage exhaust valve.
• Narcosis: Inert gas intoxication.
• Nitrogen: Inert gas making up 78 percent of air.
• Nitrogen narcosis: Intoxicating effect on a diver due to toxic levels of nitrogen in breathing gases.
• Night diving: Scuba diving done at night, usually around dusk.
• Nitrox: Mixture of nitrogen and oxygen.
• O-ring: Common seal for scuba equipment.
• Octopus: Used in place of a primary regulator during ascent.
• Off gassing: Also called "out gassing", process of releasing inert gasses, such as nitrogen, at the surface.
• Open circuit scuba: Breathing apparatus involving exhaling air into the water.
• Open water certification: Four or five open water dives are performed upon completion of a scuba diving training course, after which the diver receives a certification card.
• Open water diving: Recreational diving done in natural open waters with no overhead obstructions.
• Oxygen toxicity: Illness resulting from breathing too much oxygen.
• P-valve: Dry suit equipment allowing the diver to urinate during a dive.
• Pony bottle: Small diving cylinder used in cases of emergency.
• Purge valve: Allows mask and regulator to be cleared without having to remove them.
• Re-breather: Scuba apparatus that recycles exhaled air and prepares the carbon dioxide for re-use.
• Recreational scuba diving: Diving no deeper than 130 fsw using only compressed air and with no decompression stops.
• Dive regulator (scuba regulator): One of the most critical pieces of scuba diving gear; supplies the diver with breathable gas at ambient pressures.
• Rinse tank: Fresh water tank for rinsing dive equipment after use.
• Rule of thirds: An air management rule whereby a diver uses a third of the tank to descend, a third to resurface, and the remaining third for a buddy in case of emergency.
• Safety stop: Stopping for one to three minutes at the end of every dive in order to re-gas.
• SCUBA: Acronym for "self-contained underwater breathing apparatus".
• Scooter: Diving portal allowing a diver to navigate around objects underwater.
• SCR: Short for 'semi-closed re-breather'.
• Scrubber: Part of a re-breather system that recycles exhaled oxygen.
• Side mount diving: Divers mount cylinders on the side to allow entry into narrow passages.
• Singles: Single dive cylinders
• Solo diving: Diving alone without a buddy: usually not recommended.
• Stage bottle: Container of decompression gas used to extend dives and aid decompression.
• Snorkel: Flexible tube used for breathing underwater and close the surface.
• Surface interval: Amount of time spent on the surface between dives.
• Table 6: Navy treatment for decompression sickness.
• Tank: Slang for scuba cylinder
• Technical diving: Descending to depths beyond those of common recreational diving.
• Time to fly: It is recommended that a diver wait 24 hours after diving to fly in a plane in order to recover from the effects of decompression.
• Trimix: Mixture of helium, oxygen, and nitrogen used for deep diving.
• Upstream valve: Valve that works against, and not with, pressure.
• V-weight: Weight carried between cylinders to normalize buoyancy.
• Veering: Wind shifting into clockwise direction.
• Vertigo: dizziness caused by inner ear problems.
• Visibility ('vis'): How far a diver can see underwater.
• Wall dive: Diving near an underwater cliff.
• Wet suit: Diving suit that provides thermal and other protection from the elements.
• Wing: Back-mounted buoyancy compensator used by cave and technical divers.
• Wreck diving: Diving into natural and man-made disaster sites.
• X scooter: Very lightweight diver propulsion vehicle.
• Yaw: Swinging off course.
• Y valve: A double outlet on a tank.