Scuba diving is nothing but swimming underwater while using self-contained breathing equipment. By carrying a source of compressed air, the scuba diver is able to stay underwater longer than with the simple breath-holding techniques and is not hindered by air-lines to a remote air source. The scuba diver typically swims underwater by using fins attached to the feet.
Snorkeling
Snorkeling is the practice of swimming at the surface of a body of water while equipped with a diving mask, a shaped tube called a snorkel, and usually swimfins. Combining these tools allows the snorkeler to observe underwater attractions for extended periods of time with relatively little effort.