Florida Keys National Marine Sanctuary, Florida
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The 2,900-square-nautical mile sanctuary stretches from Key Largo, less than 50 miles from Miami, to Dry Tortugas, 70 miles west of Key West. Those needing a quick snorkel escape can hit Key Largo's John Pennekamp Coral Reef State Park, which even offers guided tours and equipment rental. Or, drive 122 miles to Key West and take the two-hour ferry to Garden Key in Dry Tortugas National Park where the only crowds are huge schools of fish. Snorkel over clouds of grey snapper and three-foot silvery tarpon along the moat wall. Grouper, barracuda, and reef fish hang out among sets of pilings left from Navy coal piers built in the 1800s. Some 30 species of stony and soft corals thrive in the warm, clear water around the island. Return on the afternoon ferry or camp on the island for a moonlight snorkel experience.