AGE- Arterial Gas Embolism: A potentially serious scuba diving injury caused by bubbles of gas in the bloodstream

AI- Assistant Instructor

AI- Air Integrated: a dive computer attached to an air supply, which provides a digital readout of remaining tank pressure. Used to supplement or replace a traditional analog pressure gauge.

ANDI- American Nitrox Divers, Inc. N.Y.-based technical certification agency.

AOW- Advanced Open Water (there is some debate over just how "advanced" it is, but that's what it stands for)

ATA- ATmospheres Absolute; 1 ATA is the atmospheric pressure at sea level, and an additional atmosphere worth of pressure is added every 33' of sea water. Atmosphere absolute = 14.7 PSI of pressure.

Bar- Metric unit for measuring pressure. A full scuba tank at 3,000 psi reads approximately 200 bar on a metric gauge.

BC- Buoyancy Compensator [Device, sometimes "BCD"] - if you don't know what this is, get certified for scuba then come back.

BOW- Basic Open Water. Not usually an actual course, but useful to distinguish a certification level below AOW.

BP/W- Backplate and Wing, a style of buoyancy compensator characterized by a rigid backplate (aluminum, steel or delrin) and a separate wing, and a streamlined front

BSAC- British Sub Aqua Club. International certification agency based in the United Kingdom.

BT- Bottom Time

BWRAF - PADI training acronym; "Begin with Review and Friend"
(aka "Big White Rabbits are Fluffy", "Blonde Women Really are Fun"), Checklist for pre-dive buddy-checks which stands for BC, Weights, Released, Air, Final check

C-card: scuba diving certification card given by a certification agency such as PADI, NAUI, SSI, GUE, etc.

CD- Course Director. Level of instructor certification authorized to conduct instructor training.

CESA- Controlled Emergency Swimming Ascent

DAN- Divers Alert Network. Nonprofit organization that provides emergency and informational advice and assistance for diving injuries, promotes diving-related medical research and education, collects injury statistics, and offers dive safety services to its members and the diving community.

DCI- Decompression Illness; a generic term for pressure-related scuba injuries including AGE and DCS

DCS- Decompression Sickness; the 'bends'

DIN- Deutsches Institut fuer Normung (German Institute for Standardization, like ISO9000 and ANSI), but in relation to scuba, it usually refers to an alternate to the yoke-style connector on a scuba tank

DIR- Do(ing) It Right, a style of diving that mixes a specific gear configuration and a style a team diving

DM- Dive Master (usually, the person running the show on a dive boat, aside from the Captain. In charge of diving operations, primarily concerned with safety.)

DPV- diver propulsion vehicle. Underwater "scooter" that allows a diver to cover an increased distance underwater.

DS- Dry suit.

EANx- Enriched Air Nitrox, sometimes simply "Nitrox". Refers to air with a higher-than-normal level of oxygen. EAN is a subset of nitrox. Nitrox is any mixture of nitrogen and oxygen, while EAN is air with additional oxygen added.

FFW- Feet of Fresh Water (ex: I dove to 25 ffw in a local quarry on my trip to Idaho)

FSW- Feet of Sea Water (ex: I only went down to 25 fsw for my first dive in Hawaii)

GUE- Global Underwater Explorers: A certification agency leading the DIR diving style. Certifies divers for cave and technical divers. Based in Florida.

HID- High Intensity Discharge, a kind of very bright bulb found in some of your better underwater flashlights

Hog- "Hogarthian". An ultra-simplified gear system developed for cave diving (originally) bu Bill "Hogarth" Main. Used as the inspiration of the DIR gear configuration.

HP- High Pressure, usually refers to a scuba tank that can be filled to pressures greater than 3000 psi without exceeding manufacture and DOT allowable limits. Often combined with the fill rating of a tank (measured in cubic feet) to describe a tank and it's capacity, for instance, an HP100 would be a high pressure tank that holds 100cf of gas when filled to it's rated capacity.

Hydro- Hydrostatic test required for scuba cylinders every five years.

IANTD International Association of Nitrox and Technical Divers. Recreational, cave and technical certification agency.

IDC- Instructor Development Course. A class or series of classes designed to advance the knowledge and skill level of divers so they can qualify as scuba instructors.

IP- Intermediate Pressure; the pressure between the first and second stages of a regulator

ITC- Instructor Training Course. Class in which divers advance their knowledge and skill, and qualify as scuba instructors.

L.A. County- Los Angeles County Department of Parks and Recreation, Underwater Unit. The oldest scuba certification organization. Still in operation today!

LDS- Local Dive Shop

LP- Low Pressure, usually refers to a scuba tank that can only be filled to pressures lower than 3000 psi without exceeding manufacture and DOT allowable limits.

MOD- Maximum Operating Depth, maximum safe depth for a specific Nitrox (or air) mix, beyond which risks of Oxygen Toxicity exceed limits generally regarded as safe.

MOF- Mask on Forehead. Just what you think... your mask on your forehead, a practice frowned upon by many. See NMOF.

NACD- National Association for Cave Diving. Trains and certifies cavern and cave divers.

NAUI- National Association of Underwater Instructors. Not-for-profit recreational and technical certification agency based in Florida.

NDL- No Decompression Limit, max time limit at a given depth without having to decompression stops, i.e., normal recreational diving

NMOF- No Mask on Forehead. Just what you think... NOT having your mask on your forehead, to avoid being frowned upon by those who dislike the practice. See MOF.

NSS/CDS- National Speleological Society/Cave Diving Section. Division of the cavers' society that trains and certifies cavern and cave divers.

OCA- Oxygen Clean Air. Regular air (~21% o2, 79% Nitrogen) that has been cleaned sufficiently so it will not contaminate tanks which have been specially cleaned for use with pure oxygen.

OOA- Out of Air

OW- Open Water. The most common designation for the initial scuba certification that results in qualification to dive without supervision.

PADI- Professional Association of Diving Instructors. Recreational certification agency based in California.

PDIC- Professional Diving Instructors Corporation International. Pennsylvania-based certification agency.

PSD- Public Safety Diver

PSI- Pounds per Square Inch, a measurement of pressure. Commonly used to determine how much gas is in a scuba tank of a known volume.

RDP- Recreational Dive Planner, PADI's regular dive tables used to determine NDLs for purposes of dive planning and logging.

RMV- Respiratory Minute Volume: The volume of gas used in one minute at a given depth, calculated based on SAC. See also, SAC.

SAC- Surface Air Consumption [Rate- sometimes SCR], a way to calculate how long your air will last at a given depth (once you know the rate at the surface, it is a simple calculation to determine it at any depth).

SAR- Search and Rescue

SDI- Scuba Diving International. The recreational scuba training and certification arm of TDI.

SI- Surface Interval, the time spent out of the water between dives, be it 5 minutes, 5 years, or anywhere in between

SMB- Surface Marker Buoy, an inflatable tube device used to attract attention at the surface. Sometimes also used as a flotation device during decompression.

SPG- Submersible Pressure Gauge, that round thing you look at to see how much air your tank has left

SSI- Scuba Schools International. Certification agency based in Colorado.

STA- Single Tank Adapter, an optional component in a bp/w system. Backplates are primarily designed for use with double tanks, so to use them with a single tank, either a wing with special stabilizers is needed or an STA. Also makes it faster and simpler to switch configurations between a doubles wing and doubles tank, and a singles wing and single tank.

TDI- Technical Diving International. Certification agency for technical dive training, based in Maine.

VENTID-C- Acronym describing possible symptoms of DCS: Vision Ears Nausea Twitching Irritation Dizziness Convulsions

VIP- Visual Inspection Program. An annual inspection required for scuba tanks.

WAI- Wireless Air Integrated. A computer with a wireless transponder to send pressure information from a small device mounted on the first stage to a separate computer, usually worn on the wrist.

WKPP- Woodsville-Karst Plains Project; cave diving group

YMCA- Young Men's Christian Association. Maintains an international scuba training and certification program, along with many other family-oriented activities.