"AAS"
=
Alternate Air Source, see Bailout.
"ABLJ"
=
Adjustable Buoyacy Life Jacket, mostly build horse-collar style, much more than just a BC (Buoyancy Compensator).
"AGE"
=
Arterial Gas Embolism, bubble causing obstruction to a blood vessel. The term Arterial Gas Embolism refers to small air bubbles in the bloodstream. This is almost always the result of a rapid ascent, with or without breath-holding, which causes the lung tissue to tear and allows air into the blood vessels.
"air hog"
=
Diver who sucks tank dry in record time. (Or in less time than it takes their buddy.)
"Ambient Pressure"
=
Pamb. = The pressure surrounding the diver/rebreather. Rough values are 1.0 bar at the surface, 2 bar at 10m, 3 bar at 20m, 4 bar at 30m etc.. When calibrating oxygen-sensors prior to diving, the ambient pressure is the current atmospheric pressure.
"APTDI"
=
"ATA"
=
"Best Mix"
=
The Breathing-Gas that offers the shortest Decompresson-Time. For Calculation you have to care about ED, END, ppO2-limits (ppO2-time-limits) and for extreme deep dives also about HPNS. In most cases the best mix for a OC bounce-dive is really not the best mix for a long rebreather dive to the same depth.
"Bailout"
=
An emergency breathing system: for example an extra cylinder of gas carried by a surface supplied diver or a rebreather diver to enable them to reach safety in the event of an interruption of their primary supply. For saturation divers, this would typically be to reach a habitat.
For a rebreather diver in most cases doing a bailout does not stand for a switch to an other breathing- system but just to an other mode, like moving from the CCR- to the SCR-mode on the same loop. But keep in mind: a loop could be unrecoverable, so take care of an alternative.
To bailout means ending the dive.
In doubt - bail out !
"BMAP"
=
B
uoyancy Mediated Airway Protection. This is a really important matter, so it has its own chapter. In my opinion a diver is only correctly equipped if he can start, with a single second of action, a process that will bring him to the surface, pull him in a face-up position and show a (not to small) signal-colour-surface. (That this can't work while being in a wreck or cave is no reason not to care about safety.) The result shall also be guaranteed if the main-bottle(s) are empty!"BOB"
=
Bailout Rebreather
"Braille dive"
=
Visibility so bad you have to just feel your way around 
"BT"
=
Bottom Time - definition is agency dependant.
"Calibration"
=
All the oxygen sensor-cells have to be calibrated before use.
"CCR"
=
Closed Cirquit Rebreather
"CNS Oxygen Toxicity"
=
Central Nervous System Oxygen Toxicity, also known as the Paul Bert Effect, tox, or oxtox. Oxygen toxicity is a combination of oxygen pressure and time. The exposure limits are shown on a separate page.
"CPR"
=
Cardio-Pulmonary Rescusitation
"CSU"
=
ANDI Complete SafeAir® User = an initial OC-Nitrox Brevet
"cu. ft."
=
Cubic feet. 1 cubic foot = 28.31685 liters. "80cu. ft." means 2265.348 bar*liter, so this tank for example has a volume of 10.74liters and is rated for a pressure of 211bar 
"DAU"
=
Dumbest Assumeable User, this abbreviation was born in Germany, the orginal words are
"DCI"
=
Decompression Illness, including DCS and AGE.
"DCS"
=
Decompression Sickness
Type I DCS: This is DCS that results in joint or muscle pain, extreme
fatigue or skin manifestations.
Type II DCS: Includes any DCS hit that has neurological or
cardio-respiratory symptoms.
"DDRC"
=
Diving Diseases Research Centre, in Plymouth, England. The leading hyperbaric treatment and research centre in Britain.
"DNAx"
=
Denitrogenated Air, means for the diver the same as EANx, but signalices that this Nitox was produced by using a nitrox-membrane (a system similar to osmotic sea-water desalting).
"DOA"
=
Dictionatry of Abbreviations. What you are reading at the moment is the
"DPV"
=
Dive Propulsion Vehicle = Scooter .
"EAD"
=
Equivalent Air Depth (used on Nitrox-Dives to look into a Decompression-Table that was printed for Air-Dives.)
"EANx"
=
Enriched Air Nitrox, EAN40 contains 40% Oxygen and 60% Nitrogen.
"ED"
=
Equivalent Density air (the depth in which Air brings the same breathing-resistance)
If someone does not care about the ED and dives a gas with too high density he risks an Esoufflement, what under diving-conditions normally also means Hypercapnia.
"END"
=
Equivalent Narcosis Depth (compares the narcotic potential of a gas with that of air)
This value may differ for the same gas if you read different authors, because some count Oxygen as not narcotic, some count it like Nitrogen and some double than nitrogen.
"end of the line"
=
Yet another caver term, used and abused by the rebrether guys when talking about extreme rebreather diving.
"fiO2"
=
Fraction in the Inhaled gas that is Oxygen
"fsO2"
=
Fraction in the Supply gas that is Oxygen.
For OC-Divers fiO2 = fsO2 , for Rebreather-Divers it is not.
"FSW"
=
Feet of Salt Water an antiquated, imperial unit of measurement for the depth or for relative pressure.
"goober-juice" or "lung-juice"
=
The disgusting slime that comes out of the rebreather- and simular hoses after a long dive.
"Halocline"
=
Boundary between layers of water of different salinities, looks like a barrier of mist.
"Hawaiian Method"
=
a method of in-water recompression (IWR).
"Heliox"
=
Breathing mix of Helium and Oxygen.
"Hogarth principle"
=
A name for the old principle that divers use since many decades: 'less is more'. It is named after
Your buddy is part of the Hogarth system, this means: strict team diving & uniform equipment constellation.
"Holistic system"
=
Teaching all subjects to all levels but more detailed to the more experanced. This means for example that also the Novice-Exam includes Medic-First-Aid.
"Hookah"
=
Regulator for breathing surface supplied air, either from a tank or a compressor, typically down to about 10m.
"Hypercapnia"
=
An excess of carbon dioxide.
"Hyperoxic"
=
Used by some folks when they just mean Situations with a ppO2 above 1.6 bar.
"Hypoxic"
=
When the ppO2 is less than 0.16 bar.
"IP"
=
Intermediate Pressure, also named LP, i.e. the pressure between the first and second stages.
"Jackadd"
=
JACK-ADD = Added Jack = BC-Device that is an add-on of Tank or Rebreather and does not offer all ABLJ safety-functions.
"keyboard diver"
=
Term for those who spend much more time typing about diving than actually doing it.
"Limeburger"
=
Diver between Rebreather and Bailout-Rebreather
"Limey"
=
A Buddy Inspiration Owner
"Liorraine Smith Effect"
=
"LP"
=
Low Pressure, also named IP, i.e. the pressure between the first and
"Lubrication"
=
(if used by Nitrox Divers it means) any approved oxygen compatible grease.
"MOD"
=
Maximum Operating Depth for a breathing gas in the given situation.
"Nagileh System"
=
"Hookah"
"NDL"
=
Non Decompression Limit = the time you can dive on a given depth, breathing a given gas without the need of a decompression-stop = "Nullzeit"
"NITROX"
=
Breathing mix of Nitrogen and Oxygen.
"NITROX-pure"
=
the Trademark under which the Messer Griesheim GmbH sells their diving-grade EANx.
"O2 clean"
=
Clean enough of combustibles such as oil to allow use with high pressure O2.
"OC"
=
Open-Circuit mode, that meas that the gas is exhaled to the environment, not into a rebreather.
"OTU"
=
pulmonary Oxygen Toxicity Unit. Oxygen toxicity is a combination of oxygen pressure and time. The exposure limits are shown on a separate page.
"Oxygen Cells"
=
Cells or Sensors used to measure/monitor the ppO2.
"P-vent"
=
Directing the vented bubbles on ascent up the neck of your wetsuit while in a heads-down position for the purpose of removing urine.
"Pamb."
=
Ambient Pressure = The pressure surrounding the diver/rebreather. Rough value are 1.0 bar at the surface, 2 bar at 10m, 3 bar at 20m, 4 bar at 30m etc.. When calibrating oxygen-sensors prior to diving, the ambient pressure is the current atmospheric pressure.
"Paul Bert Effect"
=
"Phallocline"
=
the boundary layer between "really cold!!" deep water and relatively warm surface water, the zone where your dick disappears somewhere behind your bellybutton
"Pony Bottle"
=
a small (i.e. 4Liter*200bar) tank, typically worn beside main tank, as a fully redundant emergency air supply.
"ppO2"
=
Partial Pressure of Oxygen. Some write PO2 or PPO2 instead, but what looks like chemistry formulas.
"psi"
=
Pounds per Square Inch, 14.50377psi = 1bar.
"RMV"
=
Respiratory Minute Volume. The RMV is measured in Liter per Minute, so a OC-SCUBA-Diver who is diving in depth of 30m would empty his bottles with 100 bar*l/min while breathing with an RMV of 25 l/min.
"ROV"
=
Remote operated Vehicle.
"Rule #1"
=
NEVER dive alone !
"Rule of Thirds"
=
effective breathing-gas: a third to get there, a third to get back and a third is for safety.
"SafeAir"
=
a markterm invented by Ed Betts, president of the ANDI training agency. SafeAir® is an EAN mixture between 22 and 50% Oxygen that meets ANDI gas quality specifications.
"SCUBA"
=
any type of Self Contained Underwater Breathing Apparatus, this includes Rebreathers as well as OC-Air-SCUBA.
"SEEDS"
=
The Responsibilities of the Diveleader:
- Safety
- Equipment
- Exercise
- Discipline
- Signals
"Shot line"
=
a weight with line and buoy attached to mark the location of a wreck.
"SI"
=
Surface Interval (between dives)
"Sling [Bottle]"
=
Stage Bottle
"Slobwinder"
=
a flexible shaft, used to open/close valves that can't be reached directly. It might be a better idea to confiure und train so that everything can be reached.
"Stroke"
=
Favorite term of Florida cavers which is applied to anybody who dives without proper knowledge or intelligence.
"SMB"
=
Surface Marker Buoy. Buoy with flag (on a line to diver).
"Stage Bottle"
=
a separate gas supply which is detachable from the diver.
"suction device"
=
the diver
"Regardless of the type of controls, the biggest factor in safety
is still the suction device attached to the mouthpiece."
"Thermocline"
=
the boundary between layers of water of different temperatures.
"top-to-bottom vis"
=
Underwater visibility so good you can see the wreck from the surface.
"WOB"
=
Work Of Breath, the engery you need to breath a given volume of gas.
"XBS"
=
External Breathing System = BOB (but someone also might mean a Stage)
"YANQ"
=
Yet another Newbee Question. Ok, this is not rebreather-specific and never forget:
Nitrox-Index