NEEMO
NASA Extreme Environment Mission Operations, or NEEMO, is a NASA analog mission that sends groups of astronauts, engineers and scientists to live in the Aquarius underwater laboratory, the world's only undersea research station, for up to three weeks at a time in preparation for future space exploration. Aquarius is an underwater habitat off Key Largo, Florida, in the Florida Keys National Marine Sanctuary. It is deployed on the ocean floor next to deep coral reefs below the surface. NASA has used it since 2001 for a series of space exploration simulation missions, usually lasting 7 to 14 days, with space research mainly conducted by international astronauts. The mission had cost about 500 million U.S. dollars. The crew members are called aquanauts (as they live underwater at depth pressure for a period equal to or greater than 24 continuous hours without returning to the surface), and they perform EVAs in the underwater environment. A technique known as saturation diving allows the aquanauts to live and work underwater for days or weeks at a time. After twenty four hours underwater at any depth, the human body becomes saturated with dissolved gas. With saturation diving, divers can accurately predict exactly how much time