The only underwater hotel in the United States, a former research habitat on the bottom of a mangrove lagoon at 6.4m, which you…The only underwater hotel in the United States, a former research habitat on the bottom of a mangrove lagoon at 6.4m, which you reach by diving down and swimming up into a moon pool. Two bedrooms, a common room, hot showers, and pizza delivered by a diver in a watertight case. Built in 1972 as La Chalupa, a genuine research laboratory that operated off Puerto Rico, then converted to a hotel in 1986 and named for Jules Verne. Steven Tyler and Canadian prime minister Pierre Trudeau have both stayed. NASA has used it for astronaut training. Anchorage: Inland lagoon at Key Largo, road access, not a yacht stop. Hazards: Low viz in the lagoon; you must be comfortable diving to reach the entrance. Plus