Appendix:Glossary of scuba diving

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Here is a glossary of scuba diving terms:



arterial gas embolism is a condition that can be caused by a diving accident in which a gas expands due to too rapid ascent, and a bubble and blocks the arterial flow of blood.
altitude diving 
diving at a location where the water surface is 2000 feet above sea level or higher, and which requires special dive tables or dive computers to calculate allowed depths and times for safety.
absence of oxygen caused by inhaling a breathing gas that contains no oxygen or being unable to inhale any breathing gas.
underwater breathing equipment consisting of a diving cylinder and diving regulator.
injury caused by pressure.
beach master or dive marshal 
A person on the beach who records when divers enter and exit the water. Typically used during scuba classes to keep track of the students, watch the gear, provide assistance when required.
bounce dive 
In commercial diving, bounce diving is the alternative to saturation diving. In recreational diving, a bounce dive is a descent to maximum depth and then an ascent back to the surface with the least delay, in a dive profile resembling a spike.
buddy breathing 
Two divers sharing the same demand valve, generally after an out-of-gas emergency
buddy system 
Pair or sometimes threesome of divers that dive together as a team for safety.
buoyancy compensator or BCD, or BC 
diving equipment worn by divers to provide life-saving emergency buoyancy and the ability to control ascent and descent rates.
C-card or certification card 
proof of completed diver training and evidence of experience.
carbon monoxide poisoning
usually due to compressor maintenance errors.
carbon dioxide poisoning
is due to incomplete elimination of carbon dioxide.
a machine used to increase the volume of usable air in a diving cylinder by raising its pressure.
controlled buoyant lift
a diver rescue technique.
decompression sickness
a potentially lethal diving disorder caused by bubbles of inert gases, such as nitrogen or helium, coming out of solution and becoming trapped in the tissues, organs and blood vessels of the body causing symptoms ranging from rashes to death. Also commonly referred to as DCS, or DCI Decompression Illness
decompression stop 
a pause during the ascent phase of the dive to allow safe release of inert gases from the tissues of the body and avoid decompression sickness.
decompression tables
Printed tables that provide divers with a way of avoiding Decompression Sickness by giving the maximum times that can be spent at depth, and by indicating the Decompression Stops and Surface Intervals needed for a particular depth and time profile to be carried out safely.
decompression buoy 
a small buoy on a line that divers inflate underwater to indicate their location to their boat.
dive club 
a group of people with an interest in SCUBA diving.
dive flag 
Flag used by a boat to indicate that it has 'divers down'. Comes in two versions: the international marine (international code letter flag 'A', and the red and white flag (red with white diagonal.
dive profile 
a two dimensional representation of the two most important characteristics of the dive that a diver must monitor to dive safely: depth and time. The profile is often used when describing a dive's likely decompression obligation.
dive shop 
supplier of diving equipment or training, or organizer of dive expeditions.
dive tables 
see Decompression tables.
A professional level diver who leads a group of less experienced divers underwater.
drift diving 
diving in a current.
death caused by inability to inhale anything but water.
dry suit 
a diving suit designed to thermally insulate and provide protection to the skin of the diver.
medical conditions resulting from changes in ambient pressure.
electro-galvanic fuel cell 
an electrical device used to measure the concentration of oxygen gas in diving equipment.
equivalent air depth 
a way of expressing the narcotic effect of breathing gas mixtures that contain nitrogen, for example nitrox and trimix.
A scuba diver, particularly a military diver on an undercover mission.


gas blending 
filling diving cylinders with gas mixes such as nitrox or trimix.
gas embolism 
a potentially lethal diving disorder caused by air or other gas bubbles entering the blood stream through wounds.
hard hat diving 
surface supplied diving, generally in professional diving, either wearing a modern diving helmet or the old-style standard diving dress and brass helmet.
a gas blend of helium and oxygen in which helium replaces the normal nitrogen in air allowing diving at greater depths than can be done with air.
High Pressure Nervous Syndrome or Helium Tremors - caused by using breathing gases that contain helium at depth.
carbon dioxide poisoning generally caused by rebreathing your own exhaled carbon dioxide. A big problem at depth especially with rebreathers or high rates of exertion.
either a deliberate and dangerous method intended to extend the duration of a free dive or the body's response to hypercapnia.
insufficient oxygen in the body - normally caused by inhaling a breathing gas that contains insufficient oxygen to support normal activities or consciousness.
a potentially lethal medical condition caused by cooling the body.
interstitial emphysema 
gas trapped in the chest after lung barotrauma.
An early yoke style scuba tank valve that had a lever which activated a reserve pressure release and was commonly used before the submersible pressure gauge was available.
A standard yoke style valve without a reserve lever.
kayak diving 
an alternative to boat diving or shore diving where the diver uses a special purpose kayak to get to site.
log book 
List of the dives a diver has recorded for proof of experience.


maximum operating depth 
the depth at which the partial pressure of oxygen (ppO2) of a gas mix exceeds a safe limit.
navy SEAL 
A US Navy trained military diver.
night diving 
a dive at night - many underwater animals are nocturnal or behave differently at night.
nitrogen narcosis 
condition caused by breathing nitrogen at high pressure (at depth).
a breathing gas consisting of oxygen and nitrogen
oxygen toxicity 
is caused by using breathing gases that contain oxygen at high pressure (at depth).
partial pressure of a gas 
the concentration of individual component gases of breathing gases.
collapsed lung.
professional diving 
diving for payment.
breathing equipment that captures, cleanses and re-oxygenates exhaled breath so that it can be re-inhaled.
recompression chamber 
a pressure vessel used to treat divers suffering from certain diving disorders such as decompression sickness.
recreational diving 
a type of diving that uses SCUBA equipment for the purpose of leisure and enjoyment.


salt water aspiration syndrome 
the diver inhales a mist of sea water from a fault demand valve causing a reaction in the lungs.
saturation diving 
a decompression regime used in commercial diving that allows divers to live work for weeks at a time where their tissues become saturated in high pressure gas.
secondary drowning 
can occur hours after a near drowning.
semi-dry suit 
a wet suit with wrist and ankle seals to reduce entry and exit of water.
shore diving 
Scuba diving that starts from the shore line.
a Lycra suit worn by a diver in warm water or under a wet suit.
solo diving 
diving alone - an alternative to the buddy system.
standard diving dress 
old-fashioned "hard hat" diving gear.
subcutaneous emphysema 
gas under the skin tissue.
submersible pressure gauge or SPG 
Gauge attached to the regulator and used to monitor pressure remaining in the scuba cylinder.
surface detection aids 
equipment, such as flags, SMBs, flares, EPIRBs and whistles, carried by divers to maintain contact with dive boats or attract rescue when lost at sea.
surface interval 
the time between dives. Divers need to track this time interval for planning decompression for the next dive.
surface marker buoy, SMB 
a small inflated buoy that divers tow when underwater on drift dives to indicate their location to their boat.
technical diving 
a form of SCUBA diving that exceeds the scope of recreational diving allowing deeper and longer dives.
time to fly 
Divers must wait approx. 24 hours after the last dive before flying to reduce the risk of decompression sickness.
a breathing gas consisting of oxygen, helium and nitrogen.
wall diving 
diving along the face of a vertical wall - requires good buoyancy control because there is no seabed to prevent the diver descending too deep.
wet suit 
A tightly fitting neoprene thermally-insulating diving suit that allows a limited volume of water inside the suit.
wreck diving 
diving on shipwrecks.