Discover Scuba Diving
The most elementary dive is what the Professional Association of Diving Instructors calls the Discover Scuba Dive. It is designed to give some exposure to the curious. An instructor will teach the novice diver the basics of operating scuba gear, and then take them on a shallow (less than 30 feet) one-on-one dive.
Open Water is the minimum requirement for solo diving, and there are some small differences between organizations regarding certification. However, a student can expect to spend more than 30 hours in the classroom and on controlled dives, and four open water dives before certification.
Advanced Open Water
Advanced Open Water certifies a diver for the general limits of recreational diving, which are typically expressed as a dive limit of 138 feet. The requirements vary, but usually consist of about 15 hours of course work and related dives focusing on skills like underwater navigation and buoyancy control.
Going deeper than 138 feet requires technical dive training, which focuses on using special gas mixtures and decompression techniques. The recommended limit for technical diving is 660 feet.
When the body is subjected to increased pressures underwater, the blood absorbs potentially dangerous quantities of nitrogen. Divers must take care to decompress in stages, so as to release the gas slowly, or risk developing decompression sickness (better known as "the bends").
The most popular places to dive are usually warm, tropical waters. Cold waters also offer interesting fish, undersea formations, and ship wrecks. Wherever there is something interesting under the waves, there is a good place to scuba dive.