Scuba is a type of underwater diving that uses self-contained breathing apparatus and equipment to explore marine environments. It is a recreational activity, a sport, and a profession with a wide variety of applications. Scuba can also be used for scientific research, exploration, salvage, and other purposes that require advanced training and specialized equipment.

Unlike snorkeling, which requires divers to surface regularly for air, scuba diving allows them to stay underwater for longer periods of time. Scuba can be performed in freshwater or salt water, and most divers use a wetsuit for protection against the elements and to help maintain buoyancy. A diver may also need a diving logbook to record dive details such as depth and duration.

A scuba diving trip typically begins with an orientation session wherein the basic equipment is explained and practiced. Then, the diver heads to a diving site with his or her dive instructor or guide and enters the water. Typical activities during a scuba dive include swimming through schools of colorful fish, observing marine life, and exploring underwater features such as coral reefs and shipwrecks.

The most important piece of scuba gear is the buoyancy control device (also known as a BCD or BC). Worn on the diver’s back, this device has air bladders that can be filled or released to adjust the diver’s buoyancy. It is also used to hold the tank, so that it doesn’t fall over while swimming. The diver must check his or her SPG frequently to monitor the amount of air remaining, and must also regularly signal his or her buddy to let them know when it is time to surface.