Aquarius is the only undersea laboratory in the world. It is owned by the National Oceanic and Atmospheric Administration, or NOAA, and administered by NOAA's National Undersea Research Program.

The facility is operated by the National Undersea Research Center at the University of North Carolina at Wilmington (UNCW). It provides a long-term research platform and undersea living quarters that allow scientists to stay on the seafloor for extended periods of time.

Image to right: Aquarius was reconditioned in 1996 and redeployed to the Florida Keys in 1997. The inset photo shows the laboratory on the dock before it was towed out to sea and placed in its current position at Conch Reef. Credit: NASA

Aquarius was built in Victoria, Texas, in 1986. Originally, it was deployed in the U.S. Virgin Islands, but was later moved to its current location, 3.5 miles off Key Largo in the Florida Keys National Marine Sanctuary. It stands next to deep coral reefs 62 feet below the surface.

The laboratory has hosted more than 200 scientists representing more than 90 organizations, including NASA and universities from the United States and several foreign countries. Aquarius scientists work to understand the changing ocean and the condition of coral reefs, which are threatened locally, regionally and globally by increasing amounts of pollution, over-harvesting of fisheries, disease and climate change.

Image to left: Aquarius is located in the Florida Keys National Marine Sanctuary. Credit: NASA

Science achievements from Aquarius include discoveries related to the damaging effects of ultraviolet light on coral reefs, geological studies that use fossil reefs to better understand the significance of present-day changes in coral reefs, research that is rewriting the book on how corals feed, growth studies of important sponges that uncovered surprising factors affecting their abundance and distribution, water quality studies to evaluate sources of pollution and long-term studies of reefs to distinguish between changes caused by natural system variability and humans.

The Aquarius system has three elements: a life-support buoy at the surface, the habitat and a baseplate that secures the habitat to the ocean floor. The Aquarius habitat has about 400 square feet of living and laboratory space.

Image above: Aquarius habitat diagram. Credit: UNCW

Near the habitat are other facilities to assist divers. Two waystations - the Pinnacle and the Gazebo - hold pockets of air. Divers can stop at these locations to top off their air tanks and talk.

Aquarius is an ambient pressure habitat, which means that the interior atmospheric pressure is equal to the surrounding water pressure. Its main entrance in the Wet Porch remains open to the ocean, and water is kept out by the equivalent air pressure inside, much like an air pocket inside an inverted glass prevents water from completely filling when immersed.

The baseplate rests in approximately 62 feet of water, with the habitat mounted off the bottom at a depth of approximately 47 feet - tidal range at the site is between 2 and 3 feet. This operating depth is referred to as "hatch depth."

Image to right: A diver crouches inside the Pinnacle waystation, where he can catch a breath of fresh air and top off his tanks. Credit: NASA

The pressure at 47 feet of seawater is about 2.5 times greater than the atmospheric pressure found at sea level. At this depth and pressure, visitors to Aquarius have only about 80 minutes to complete their stay and return to the surface before they risk experiencing decompression-related illness.

However, the mission inhabitants of Aquarius, known as "aquanauts," can stay indefinitely and have nearly unlimited bottom time during their scuba dives from Aquarius. At the end of a mission, aquanauts undergo a 17-hour decompression that is conducted within Aquarius itself, while on the bottom. At the end of decompression, aquanauts exit Aquarius and scuba-dive back to the surface.

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