By Jim Kittrell

Divers often joke about whether they are "certified" or just "certifiable." Often the answer is both. Here’s what you need to know to join this offbeat tribe.

Can You Handle It?
Experienced divers actually try not to swim very much (to conserve air), but it is important to be comfortable in the water and in reasonably good shape. During the certification course you will need to complete a 200-yard nonstop swim (no time limit) and a 10-minute tread/float. Most courses also will require you to complete a fairly comprehensive medical form, so you might want to schedule a physical exam prior to enrolling.

Essential Skills
There are basically two ways to get yourself underwater with a breathing apparatus. One is to take a certification course from one of the sport’s major organizations, PADI (Professional Association of Dive Instructors) or NAUI (National Association of Underwater Instructors). The 20-hour course includes classroom, pool, and open-water components, and will set you back about $400, but the certification is valid for life. You’ll learn such vital skills as how to clear your mask when it fills with water, what to do if you’re low on air, and how to reinsert your regulator if it falls out of your mouth.

Option two is to take a "resort course," which permits you to dive with an instructor down to a maximum depth of 10 meters (33 feet). Our advice: Try the latter on your next tropical vacation to see if you like the sport before investing both time and money on training.

Gear Up
Dive gear falls into two categories: required and gadget. Required gear includes a mask, snorkel, fins, buoyancy compensator (BC), regulator, dive computer or watch, weights, and often a wetsuit. Gadget gear is usually associated with a particular type of diving--night diving, underwater photography, or search and recovery--and includes knives, underwater slates, cameras, strobes, video recorders, lights, lift bags, lines, reels, and even underwater laser pointers.

A mask, wetsuit, and fins are worth owning because a proper fit makes all the difference. For convenience we recommend you rent a tank, BC, and regulator. The quality of rental equipment at most professional dive shops is generally pretty high. If you already own a BC, and don’t mind traveling with the extra 4 pounds, then bring your own.

Speak the Language
BC: Short for buoyancy compensator, a jacket-like device that secures a tank to the diver’s back. It can also be inflated or deflated to allow divers to become neutrally buoyant.

Regulator: A mouthpiece unit that attaches to a diver’s tank. The regulator includes a primary mouthpiece, an alternate mouthpiece (often called an "octopus"), a pressure gauge (to measure the amount of air in the tank), and a depth gauge.

Dive tables: A series of charts used by divers to plan appropriate depths and times for given dives. Dive computers are electronic versions of the tables that can be taken underwater.

The Bends: Layman-speak for "decompression sickness," a painful and sometimes fatal injury caused by spending too much time too deep or by surfacing too quickly.

Hand signals: A universal underwater language. The most common signals are "thumbs up" for ascend, "thumbs down" for descend and the "OK" sign. Creative divers also have informal hand signals, ranging from "Shark!" to "I’m nervous" to "Come here you $%$!@!"

Jim Kittrell is the co-editor of Down Time, a collection of essays about the joys of scuba diving.