An aquanaut is any individual who remains underwater, exposed to the ambient pressure, long enough to come into equilibrium with his or her breathing media. Usually this is done in an underwater habitat on the seafloor for a period equal to or greater than 24 continuous hours without returning to the surface. The term is often restricted to scientists and academics, though there were a group of military aquanauts during the SEALAB program. Commercial Divers in similar circumstances are referred to as Saturation Divers. An aquanaut is distinct from a submariner, in that a submariner is confined to a moving underwater vehicle such as a submarine that holds the water pressure out. Aquanaut derives from the Latin word aqua ("water") plus the Greek nautes ("sailor"), by analogy to the similar construction "astronaut".