The warm waters off Cuba’s coast are populated by more than 900 species of fish and crustaceans—from octopus, crabs, turtles, and lobsters the size of house cats to sharks, tuna, and their cousins the billfish, which aerodynamically approach swimming perfection. The sailfish (a type of billfish) has been timed swimming over short distances at 110 kilometers per hour—faster than the cheetah. Unlike other fish, they are also warm-blooded, with temperatures considerably higher than those of the water around them.

The lucky diver may also spot whale sharks (the largest fish in the world) and manta rays up to seven meters across.

Fish to avoid include the fatally toxic and heavily camouflaged stonefish and the beautiful orange-and-white-striped lion fish, whose long spines can inflict a killer sting. The bulbous puffer, which can blow itself up to the size of a baseball, is also poisonous. Jellyfish are common, too, including the lethal Portuguese man-o’-war. And don’t go probing around inside coral, where moray eels make their home—their bite can take your fingers off.

Inland, the waters of Zapata harbor the rare manjuarí, the Cuban “alligator gar” (Atractosteus tristoechus), a living fossil.