Ambergris Caye

Coral reef systems around the world are under threat; in fact, it's estimated that one-third of all coral reefs in the world may be damaged beyond repair. Nestled in the crook of the arm of Central America is one of the world's most stunning examples of a living, breathing, thriving coral reef—an exquisitely fine-tuned ecosystem that experts say is under threat from rampant development and the destruction of critical mangrove habitat. The degradation of Belize's coral reef would have serious repercussions: The Belize Barrier Reef Reserve System, named a UNESCO World Heritage Site in 1996, is the longest continuous barrier reef in the Northern Hemisphere, 306km (190 miles) of rich and diverse marine habitat less than half a mile offshore. The diving and snorkeling along this reef is first-class, and the water quality and visibility are consistently excellent. It's a vital life source for marine species and a significant habitat for such threatened species as marine turtles, manatees, and the American marine crocodile. It is also the country's top tourist attraction. In 2009, after UNESCO officially placed the reef on its Danger List, the Belize prime minister called it a "wake-up call" for the country.

Among the hundreds of sand cays and atolls strung along Belize's coral reef, the largest island, Ambergris Caye, enjoys a prime position in this marine ecosystem: The island's 40km (25-mile) shoreline runs almost parallel to the barrier reef. Just 15 minutes by puddle jumper from Belize City, Ambergris Caye is the most developed island in the country, home to most of the cays' lodgings and restaurants. But don't expect high-gloss hospitality: A trip to Ambergris Caye is a journey back to an old-fashioned Caribbean, leisurely and laid-back. If a road is paved at all, it's paved with cobblestones. It has neither glitzy nightlife nor megaluxe resorts, but you can get a cold bottle of the local lager, Belikin, for about $2. Ambergris Caye doesn't even have classic Caribbean beaches, more like short spurts of white sand between mangrove forests and sea. Wade into the shallows, and you're up to your ankles in sea grass.

The fishing village of San Pedro (pop. 7,000) has grown to be the largest town on Ambergris Caye. This is where the action is—the island hub for restaurants, cafes, and nightclubs—and where most of the islanders live. San Pedro has a funky, joyful vibe, where the sandy streets are filled with bicycles and golf carts, and the occasional taxi.

As for the lack of big, wide classic beaches, do as the locals do: Swim off one of the many piers that extend beyond the sea grass. Or do your swimming during your forays to the coral reef, when you'll be immersed in warm, sparkling blue waters.

The coral reef is the major draw for visitors, and Ambergris has incredibly easy access to world-class dive and snorkel sites. Shark-Ray Alley and Hol Chan Marine Reserve are two justifiably popular snorkel spots just off the island, where close encounters with green moray eels, groupers, stingrays, and nurse sharks are abundant. Both sites are about 6.4km (4 miles) southeast of San Pedro Town. For reliable scuba diving service, contact Amigos del Mar (☎ 501/226-2706; www.amigosdive.com) qua Dives (☎ 800/641-2994 in the U.S. and Canada, or 501/226-3415; www.aquadives.com) or Gaz Cooper's Dive Belize (☎ 800/499-3002in the U.S. and Canada, or 501/226-4455; www.divebelize.com) Among the operators who specialize in snorkeling trips here is the very personable Alfonse Graniel and his launch Li'l Alfonse (☎ 501/226-3537;