Almost 70 miles (113 km) west of Key West lies the remote Dry Tortugas National Park. The 100-square mile park is mostly open water with seven small islands. Accessible only by boat or seaplane, the park is known the world over as the home of magnificent Fort Jefferson, picturesque blue waters, superlative coral reefs and marine life, and the vast assortment of bird life that frequent the area.
For more information on visiting Dry Tortugas, follow this link-
http://www.nps.gov/drto/index.htm
The Dry Tortugas are a small group of islands, located in the Gulf of Mexico at the end of the Florida Keys, United States, about 67 miles (108 km) west of Key West, and 37 miles (60 km) west of the Marquesas Keys, the closest islands. Still further west is the Tortugas Bank, which is completely submerged. The first Europeans to discover the islands were the Spanish in 1513, led by explorer Juan Ponce de León. They are an unincorporated area of Monroe County, Florida, and belong to the Lower Keys Census County Division. With their surrounding waters, they constitute the Dry Tortugas National Park.