Scuba is a fun recreational activity, has military and commercial applications, and allows scientists to access underwater habitats that are inaccessible otherwise. Divers must be properly trained to use the equipment, and must understand the basic principles of physics and marine biology in order to dive safely.

The first scuba dive is usually at a safe pool or shallow bay where an instructor will explain how all the gear works before entering the water. New divers are often apprehensive about breathing through the regulator while they are under water, but after a few attempts they will soon adapt to this unusual mode of diving.

Once a diver is in the water, they must pay careful attention to their dive plan and remain within the safe limits set by their diving organization or the local dive center. A diver must also be cautious about their movements so they do not inadvertently damage coral reefs or other sensitive habitats located at deeper depths.

Besides the normal precautions of safety, many scuba divers have an interest in the exotic sealife they encounter while on a dive. This can include octopuses with their chameleon-like ability to blend in, jellyfish that shoot their stinging cells through transparent bell bodies, or bristle worms covered in hundreds of tiny tube feet that allow them to crawl on land and through water alike.

Divers are trained in emergency procedures for dealing with the most urgent situations under the water. This includes the correct way to donate and receive breathing gas in an emergency, and how to make a controlled or uncontrolled emergency ascent from the ocean floor.