Coral reefs, like this one off the shore of St. Thomas, are formed by thousands of tiny invertebrate (no bones) animals which leave behind a limestone shell when they die. Other tiny animals latch onto these shells, die, leave behind more limestone and so on, until a reef is formed. Reefs are rich with sea life because some fish eat the tiny invertebrate animals and other fish eat the fish who eat the tiny invertebrate animals.

Scuba stands for Self-Contained Underwater Breathing Apparatus. It was invented by two Frenchmen, Jacques-Yves Cousteau and Emil Gagnan in 1943. Yes, that Jacques Cousteau. He didn't just make lots of underwater documentaries. He INVENTED Scuba!

Sport divers seldom go deeper than 130 ft (40M) because of the "bends". At that depth and beyond, pressurized air is quickly absorbed into the bloodstream and a fast ascent has an effect similar to popping open a well-shaken can of soda pop. The bubbles foam up in the blood, collecting at joints and often crippling the diver.