Scuba is an acronym for Self-Contained Underwater Breathing Apparatus, and it’s used in slang to refer to the special equipment that allows people to swim underwater. But getting scuba-certified isn’t just a matter of donning the gear and diving in: It takes lessons and practice to learn how to dive safely and responsibly.

During scuba training, students rehearse and demonstrate equipment-related skills in a pool before graduating to open water dives. They also learn about the effects of increased water pressure and how to respond in the event that their breathing gas supply runs out. The course often includes lessons in the use of hand signals to communicate with fellow divers, as well as basic dive planning such as choosing an entry and exit point that will allow them to stay within no-decompression limits.

The most important piece of scuba equipment is the mask, which must fit well and seal tightly to prevent leaks and ensure a clear view underwater. A mask with a anti-fog coating is best, and rubber is generally preferred to silicone for comfort and durability. A properly fitted snorkel is vital for efficient air exchange, while a wetsuit made of limestone-based neoprene provides warmth and buoyancy.

Once a diver has earned certification, she or he can join dive guides to explore marine life and underwater landscapes. Some divers choose to become advocates for ocean conservation by participating in reef clean-ups or citizen science projects. Others simply enjoy the opportunity to spend time in a world that is usually hidden from sight.