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Introduction

Diving (underwater), act of entering water and remaining below the surface to explore, to work, or simply to have fun. Diving is popular all over the world. It is usually done in the ocean, but divers also explore other bodies of water, including lakes, rivers, and ponds. Snorkeling on the surface (or just below) is a common form of diving, but many people use scuba, which stands for self-contained underwater breathing apparatus. Scuba divers carry a tank of air that allows them to breathe while deep underwater.

Throughout history, people have been fascinated by life underwater, and the Professional Association of Dive Instructors (PADI) estimates that there are now 6 million active divers worldwide. They engage in many different types of diving, of which wreck, cave, commercial, and military diving are just a few. The most common form of diving is sport diving, or recreational diving, which is practiced at depths of less than 130 ft (39 m). From these depths, divers can make a straight ascent to the surface. Diving beyond this limit requires advanced training.