Ambergris Caye and San Pedro

At 25 mi (40 km) long and 4½ mi (7 km) wide, Ambergris is the queen of the cayes. On early maps it was often referred to as Costa de Ambar, or the Amber Coast, a name supposedly derived from the blackish substance secreted by sperm whales—ambergris—that washes up on the beaches. Here the reef is just a few hundred yards from shore, making access to dive sites extremely easy: the journey by boat takes as little as 10 minutes. Coast and coral are farther apart as you head south, which means a greater dependence on weather. Because Ambergris Caye was the first to cater to those hoping to witness Belize's undersea world, it's generally superior in the number of dive shops, experience of dive masters, and range of equipment and facilities it offers. San Pedro even has Belize's only hyperbaric chamber and an on-site doctor to tend to divers with the bends. Most dive shops are attached to hotels, where the quality of dive masters, equipment, and facilities can vary considerably.