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Declared a marine reserve in 1998, the 61-sq-mile Caye Caulker Marine Reserve includes the portion of the barrier reef that runs parallel to the island, as well as the turtle-grass lagoon adjacent to the Caye Caulker Forest Reserve. It is rich with sea life, including colorful sponges, blue-and-yellow queen angel fish, Christmas tree worms, star coral, redband parrotfish, yellow gorgonians and more.

Between April and September, snorkelers and divers might even spot a turtle or a manatee. All local snorkel and dive operators lead tours to the Caye Caulker Marine Reserve.