Scubadiving Terms you might want to know about!

| A | B | C | D | E | F | G | H | I | J | K | L | M | N | O |
| P | Q | R | S | T | U | V | W | X | Y | Z |

A

AGE
Arterial gas embolism; lung over expansion injury caused by holding your breath while ascending allowing air bubbles into the bloodstream that block its flow. (Any foreign object in the bloodstream capable of blocking flow is an embolism.)

Alpha flag
 A blue and white flag recognized as an International Maritime flag. It indicates a vessel with limited movement, as with diver or divers below.

AP
Absolute Pressure

Apnea
Cessation of breathing

ASL
American Sign Language - one of the languages used by deaf people and sometimes by divers for communicating with hand signals

ATA
Atmospheres Absolute

ATS
Atmospheres Absolute Over Sea Level (ie gauge pressure)

AOW
Advanced open water certification; second level of certification for some agencies

B

Bail out bottle
A tank with an emergency supply of breathing gas suitable for one's depth (remember that oxygen is toxic at depth).  It bails one out of trouble with air supply, hence the name.

Bar
Short for barometric pressure? the method of measurement of air pressure used throughout most of the world and by the compressed gas industry.  (see psi)

BC or BCD
Buoyancy Compensator or Buoyancy Compensating/Control Device. Inflatable device worn when scuba diving to assist with adjusting buoyancy.

Boyle's Law
At a constant temperature, the volume of a given mass of gas is inversely proportional to the absolute pressure; if the pressure goes up the volume goes down and vice versa

Bradycardia
Slowing of the heart, triggered by cold moisture on the face while breath holding

BT
Bottom Time a measurement or calculation of the amount of time spent on a dive

Buddy
Your diving partner while diving

Buddy breathing
Two divers sharing air from one second stage regulator or one breathing from a safe second stage

Bugs
Lobsters

Burst disk
A part of a tank valve that prevents the pressure in a scuba tank from exceeding maximum operating pressure by bursting and venting the tank.

C

Carotid-sinus reflex
Tight hood or wet suit causing pressure on the carotid arteries can give a false high pressure signal and slow the heart unnecessarily: carotid-sinus receptors send impulses to the cardio inhibitory center of the brain

CCBA
Closed Circuit Breathing Apparatus, a rebreather, a device that reuses air by scrubbing or removing the carbon dioxide from it. There are usually no bubbles emitted.

Cattle boat
A term used to describe a crowded dive boat, where the divers are like a herd of cattle.

C-card
Scuba diving certification card

Charles' Law
Temperature has a direct relationship on pressure and or volume; heat will make the pressure increase, heat will also make a flexible object increase in size

Chumming
One of many euphemisms for vomiting from seasickness as well as attracting sharks with a mixture of blood and fish parts

CNS
Central Nervous System

Conduction
Transmission of heat via direct contact. Divers are most affected by conduction --- water conducts heat 25 times faster away from a person's body than air

Convection
Transmission of heat via fluids. Water is warmed by a person and rises, replaced by cooler water.

CPR
Cardio-Pulmonary Resuscitation

D

Dalton's Law
The total pressure of a gas mixture is equal to the sum of the pressures of each of the different gases making up the mixture

DAN
Divers Alert Network; non-profit member organization that does diving research and promotes diving safety

DCI
Decompression illness

DCS
Decompression sickness, caissons' disease, or the bends; pressure related injury caused by absorbing excess nitrogen under pressure while diving; if coming up to fast or staying down too long the nitrogen will form bubbles after or during ascent that will cause pain or ill feeling or other symptoms; a common symptom is pain in the joints causing atypical bending, hence the term "the bends"; symptoms may not appear until days later

Decompression
The release of nitrogen from the tissues into the bloodstream and out through the lungs

Dive flag, Diver down flag
The dive flag used predominantly in the United States. It is not recognized internationally yet is the one most used by American divers. It is required to be used by them in many states and locales when they are diving, and many locales have laws prohibiting boaters and others from approaching within a specified distance.

DIN
Deutsches Institut fuer Normung - German Institute for Standardization an organization that has set many standards, including in electronics. When used in diving, it usually refers to DIN valves on tanks which are a more secure design

Dive tables
A set of numbers that indicate the maximum time one may remain at a particular depth without going into stage decompression diving, thereby remaining within the no-decompression limits (NDL)

DM
Divemaster

DO
Diving Officer

DPV
Diver Propulsion Vehicle, an underwater scooter used to pull divers through the water (which conserves their air).

Drift dive
A dive made at a location (such as Cozumel, Mexico) where the current can carry a diver along without finning being necessary.

E

EAN
Enriched Air Nitrox; air mixture with oxygen content above 21 per cent

F

FFW
Feet of fresh water

FSW
Feet of salt water

First stage
Generally refers to the part of the regulator that attaches to the tank valve (see second stage)  can also be part of stage decompression diving

G

Goodie bag
Mesh bag with locking wire frame used to carry goodies (see bugs) underwater

H

Henry's Law
The amount of gas that will dissolve into a liquid at a given temperature is almost directly proportional to the partial pressure of that gas

HPNS
High Pressure Nervous Syndrome - a nervous disorder caused by breathing air under high pressure, as in underwater habitats

HP
High Pressure

Hookah
A surface compressor supplying air via hoses to one or more divers

Hypercapnia
Excess carbon dioxide caused by diver failing to breathe slowly and deeply or by heavy exertion. Headache may occur and may result in loss of consciousness.

Hypocapnia
Insufficient carbon dioxide caused by voluntary or unintentional hyperventilation. Carbon dioxide is what stimulates the breathing action --- if not stimulated by carbon dioxide build up to breath a diver or skin diver could use up more oxygen than he should and could cause shallow water blackout when ascending.

Hypoxemia
Not enough oxygen in the bloodstream

Hypoxia
Not receiving enough oxygen

I

Immersion diuresis
When immersed a person will cool down causing constriction of the blood vessels, the blood flow will be sent to the main organs, away from the legs and the body will sense an increase in fluids and send a signal to get rid of some fluid, causing one to urinate

J

J valve
A valve with a spring loaded mechanism that allows a reserve of air in the tank that can be actuated by pulling a lever secured to the valve.

K

K valve
The standard valve in use today. Both J and K valves took their names from the 1954 U.S. Divers catalog where they were items J and K. Both J and K valves are yoke valves, which refers to their attachment method.

L

Lift bag
Bag used to lift heavy objects underwater by filling the inverted bag with air and using its buoyancy to lift the object

Live aboard
A diving boat that one stays on (lives aboard) as opposed to staying in a hotel

Log book
A record of one's dives, including details of the dive. required by some operators as proof of experience

LP
Low Pressure

M

Mediastinal Emphysema
Aair expansion injury; air accumulates in the chest pressing on the heart and major blood vessels, interfering with circulation and the person may feel short of breath

MFW
Meters of fresh water

MSW
Meters of salt water

N

Narced
Nitrogen narcosis; under the influence of nitrogen while diving

NDL
No Decompression Limit - the maximum time one may stay at a particular depth in order to avoid decompression diving.

NEDU
Naval Experimental Diving Unit (U.S.)

NERC
National Environment Research Council (UK)

Nitrogen Narcosis
A narcotic or intoxicating effect caused by nitrogen at depth as pressure increases

NITROX
Any gas mixture of nitrogen and oxygen; though most commonly used for oxygen mixtures above the normal 21 per cent

NOAA
National Oceanic and Atmospheric Administration (U.S.)

NRMI
Naval Medical Research Institute (U.S.)

O

Octopus
Extra second stage regulator used by your buddy in an out of air emergency

Off-gassing
See decompression

OSHA
Occupational Safety and Health Administration (U.S.)

OW
Open water certification; first certification level

P

Pneumothorax
Air expansion injury; collapsed lung caused by air in the pleural cavity; symptom would be coughing up blood

Pony bottle
An auxiliary cylinder with an additional supply of air, an alternate air source with its own regulator

PP
Partial Pressure

PSI
Pounds per square inch; pressure measurement (see bar)

Purge valve
A valve on a snorkel, mask or regulator that allows it to be cleared of water

R

RDP
Recreational Dive Planner - a dive table for sport divers developed by PADI

REG
egulator

ROV
Remotely Operated Vehicle, often carrying cameras

S

Safe second
See octopus

SCBA
Self-Contained Breathing Apparatus, such as what firefighters use

SCUBA
Self-Contained Underwater Breathing Apparatus

SCUDA
Self Contained Underwater Drinking Apparatus. Product attached to the second stage that can be used to drink underwater.

Second stage
The part of the regulator that one breathes from (see first stage)

SI
Surface Interval - the time between dives that allows for sufficient off-gassing

SIT
Surface Interval Time - same as above.

Six pack
A term used to refer to a small (American) dive boat, where Coast Guard regulations only allow a maximum of six passengers

SLAM
Scuba Lifesaving Accident Management course by the YMCA

SPG
Submersible Pressure Gauge - a gauge attached by a hose to a first stage and indicating remaining air pressure in a tank.

Stab jacket, stabilizer jacket
A jacket style buoyancy compensator.

Stage bottle
A reserve supply of breathing gas not carried with the diver.  an example is a stage bottle at the safety decompression stop at 10-15 feet (approximately 3 to 5 meters) for divers who are low on air at that point.

Subcutaneous emphysema
Air expansion injury; air in the soft tissues at the base of the neck, person could feel a fullness in the neck and experience a voice change.

T

Tables
See dive tables

Thermocline
Thermoclines are layers of water of different temperatures felt when a transition to water of a different temperature (usually colder when descending) is made.

U

USN
United States Navy

V

VIS
Visibility underwater

W

Wall dive
Massive coral heads that extend from the depths are referred to as walls, hence diving near them constitutes a wall dive

Wet suit warmer
A humorous term referring to urinating in a wet suit and the resulting momentary warmth.