Scuba is a recreational activity in which scuba divers explore underwater environments using self-contained diving equipment. Typically, the diver wears a wetsuit and dives to observe sea life or natural features such as reefs, caves, walls and drop-offs. Diving is also used to investigate shipwrecks and other man-made structures.

In addition to the scuba gear, the scuba diver needs to be trained in proper diving techniques. This includes the ability to make safe and controlled descents and ascents, and to manage air supply (including learning how to use the demand valve to reclaim trapped air in case of an emergency). Divers must also learn how to clear water from their masks and to replace a dislodged snorkel tube. They must understand the importance of buoyancy control and how to safely use hand signals to communicate with their scuba buddy when underwater.

Scuba is a very popular sport, partly due to its accessibility and affordability. With proper training, there is little danger in scuba diving. However, it is not without risks and a variety of medical problems can arise including sunburn, seasickness and dehydration. Despite these potential hazards, diving is much safer than such sports as golf, skiing and bowling. This is mostly because divers are not as physically active as participants in those sports and the scuba gear makes them more independent of surface oxygen supplies than free swimmers. Diving can also provide a positive psychological benefit as it provides a unique opportunity to explore a part of the world that is otherwise inaccessible.