Located in the Atlantic Ocean and Biscayne Bay, the largest marine park in the US was established in 1980 to help protect a 275sq mi area of coastal wetlands, mangrove shorelines, coral reefs and a string of barrier islands. The reefsaaa are located about 10mi offshore, where warm Gulf Stream currents nurture some 50 species of living coral. For those wishing to explore the reefs, the park sponsors boat tours (reservations: b 305-230-1100) and rents scuba and snorkeling gear.