Aquamarine waters, a kaleidoscope of corals, undeveloped sandy beaches, and a 19th-century fort beckon visitors to one of the most remote national parks in the United States. Seventy miles (114 km) west of Key West, Florida, a cluster of seven small islands constitutes Dry Tortugas National Park. Only accessible by ferry, seaplane, or private charter, these remote islands offer world-class snorkeling, rare birdwatching, and secluded camping.