Aquarius was built in Victoria, Texas, in 1986 by Perry Submarine Builders and Victoria Machine Works. Its original name honored George F. Bond, the Navy physician who pioneered saturation diving and fathered the SEALAB program. The habitat was first intended for deployment off Catalina Island, California, then moved to the U.S. Virgin Islands. Hurricane Hugo battered it in 1989, forcing a retreat to Wilmington, North Carolina, for repairs. In 1993, Aquarius found its permanent home on the seafloor off Key Largo, nestled beside Conch Reef at a depth ideal for studying the health of the Florida Keys' sensitive coral ecosystems. NOAA owned and operated the facility through the University of North Carolina Wilmington until 2013, when Florida International University took over operations. FIU assumed full ownership in October 2014, making the Medina Aquarius Program the heart of its marine research initiative.

The habitat consists of three compartments, each serving a distinct purpose. The wet porch opens directly to the ocean through a moon pool, where hydrostatic equilibrium keeps air pressure matched to the surrounding water - about 2.6 atmospheres. The main compartment, strong enough to maintain near-normal atmospheric pressure like a submarine hull, holds bunks, laboratory equipment, computers, and the small galley where aquanauts process samples without ever returning to the surface. Between them sits the Entry Lock, an airlock where personnel wait while pressure adjusts between the two environments. Four scientists and two technicians can live aboard during a typical mission. The magic of saturation diving makes it possible: after twenty-four hours at depth, the human body becomes fully saturated with dissolved gas, and decompression time remains the same whether you have been down for two days or two weeks. When a mission ends, the crew spends seventeen hours inside the main compartment as pressure slowly drops, decompressing in place before ascending to the surface without needing a decompression chamber.

Living beneath the ocean carries risks that no amount of engineering can fully eliminate. During Hurricane Gordon in 1994, a generator fire forced the crew to evacuate, climbing a rescue line to the churning surface above. Hurricane Georges nearly destroyed the habitat in 1998, snapping a leg joint and shoving heavy weights across the wet porch. Both Georges and Hurricane Mitch that same year obliterated the exterior way stations where aquanauts refilled their scuba tanks. Hurricane Irma in 2017 ripped the life support buoy from its moorings and blew it to the Lignum Vitae Channel, damaging the living quarters and wet porch. Remarkably, no scientists or staff have ever been injured by storm activity at Aquarius. Budget storms proved nearly as destructive: NOAA cut funding after September 2012, and the last NOAA-sponsored mission that July included pioneering ocean explorer Sylvia Earle among its aquanauts. The daily comic strip Sherman's Lagoon ran a two-week series on the potential closing. In January 2013, Florida International University stepped in to keep the world's last undersea habitat alive.

NASA recognized in Aquarius something familiar: the closest analog on Earth to living in space. The agency's NEEMO program - NASA Extreme Environment Mission Operations - has sent astronauts to live in the habitat, testing equipment and procedures for future missions to asteroids and Mars in conditions that mimic the isolation, confinement, and hostile environment of spaceflight. Fabien Cousteau, grandson of Jacques, completed a record-breaking 31-day mission at Aquarius in 2014, surpassing his grandfather's 30-day record set aboard Conshelf in the Red Sea in 1963. The extended stays that saturation diving allows have yielded observations impossible from the surface - nine-hour dive windows that let scientists track nocturnal reef behavior, monitor spawning events in real time, and document the slow decline of coral ecosystems with an intimacy that brief visits cannot achieve. In a world that has mapped the surface of Mars in greater detail than the ocean floor, Aquarius remains a stubborn, vital reminder that the frontier begins just sixty feet below the waves.