The external envelope (main body) of Aquarius is made of 3/4" thick steel. This is the pressure hull that divides the entry
 lock and main lock. A 3/8" thick layer of insulation is located on the outer hull of Aquarius.Aquarius consists of three main
 compartments: main lock, entry lock and wet porch. The two locks are part of the 33 foot long, 9 foot diameter steel tube.
 The wet porch is a 7 foot long x 10 foot wide by 8 foot high steel box. They connect together by watertight doors.
The wet porch is open to the sea through its floor.

First, where will the underwater laboratory operate? Water depth determines the thickness of the walls and viewports, 
the type of fittings for connections and plumbing, and much more. Depth also determines what kind of breathing gas 
system is required. Most people are surprised to learn that you can only breathe normal air down to a certain depth 
before it becomes toxic. Both nitrogen and oxygen cause problems when the pressure gets too high.

Aquarius consists of more systems them just the underwater laboratory on the bottom. The habitat itself, when full of air, 
floats! Therefore, it is attached to a 120 ton baseplate that serves to anchor it to the bottom. There is also a buoy, 
called the LSB (Life Support Buoy, that is moored above Aquarius. The LSB contains generators (for power) and 
compressors (for air). The buoy is connected to the habitat by an umbilical - a set of wires and hoses wrapped together 
in aspecial protective cover. The buoy also has radios that can send signals from Aquarius to the mission control - over
nine miles away in Key Largo, Florida.

Another important consideration is related to want you want to accomplish using an underwater laboratory. In other words, 
why build an underwater habitat? In the past forty years, over sixty underwater laboratories were built, some were
 larger and some were smaller than Aquarius. Aquarius was designed to be more than just an underwater habitat for 
living. It is an underwater laboratory with wet and dry lab space, electrical and computer capabilities, and a comfortable 
iving space for six people that allows the scientists to focus on their research. The Aquarius program is less about what 
happens inside the underwater laboratory. Instead, the value of Aquarius is defined by the work scientists do outside
 Aquarius, on the reef and in the surrounding ocean.

The Aquarius System

The fully equipped underwater laboratory includes several components. The Aquarius "habitat" module is an 82-ton
 double-lock pressure vessel that measures approximately 14-meters long by 3-meters in diameter. Scientists live and 
work inside the habitat when they are not on excursions, diving outside on the reefs. Entry is through the 20-m3 wet porch, 
which contains an open moon pool, dive equipment storage areas, and hot water heater and shower. There are two main
 compartments in the Aquarius module. The 14-m3 "entry lock," contains bench space for computers and experiments, 
power equipment, life support controls, small viewports and bathroom facilities. The largest living space is the 40-m3
 "main lock." It includes berths for the six-person crew, computer work stations, two large viewports, kitchen facilities that
 include a microwave, instant hot water dispenser, refrigerator, sink, and dining and work areas (Figure 4: low res/high res). 
The main lock also contains life support controls, so both the entry and main locks can be independently pressurized.

The Aquarius baseplate is a 116-ton structure that provides a stable and level support base for the habitat. Each of 
the four legs contains 25 tons of lead ballast. The legs have seven feet of adjustment for leveling in variable seafloor
 terrain through the use of hydraulically-driven screw jacks. The habitat and baseplate were designed to survive severe 
storm conditions and have successfully weathered hurricanes in both the Caribbean and Florida.

The Life Support Buoy (LSB) is a 10-meter diameter buoy (Figure 5: low res/high res) that was provided by NOAA's 
National Data Buoy Center. The LSB is maintained above Aquarius on a five-point mooring using 2 and 5/8 inch diameter 
double-braided nylon lines connected to approximately 1.5-meter diameter spring buoys. Mooring plates were installed
 with anchor bolts grouted 1.2-meters into the seafloor. The LSB includes a communication tower and over 70-square meters
 of inside work space. Inside are two diesel-powered 40 kW generators, two 18.7 cfm air compressors, VHF radios, a cell 
phone, and a microwave broadcasting system. The LSB is linked to Aquarius by a three-inch diameter 42-meter unitized 
umbilical, which contains hoses that supply air from the compressors and oxygen from storage flasks, power lines from the
 generators, and 2 coaxial cables and 12 twisted pair wires for data and communications. The microwave telemetry system
 provides reliable audio, video, and data transmission between Aquarius and shore using "Wave Wireless Networking."
 Wave Wireless is a telecommunications and data communications manufacturer, and the specific system used is their
 SPEEDLAN 10ptp wireless link. The SPEEDLAN 10ptp is a 10-Mbps wireless point-to-point bridge that provides a 
secure wireless connection between Aquarius, the LSB, and shore. System upgrades are planned to increase 
bandwidth for improved video and voice communications that will support new broadcast and education programs.

Aquarius missions typically last 10 days. We conduct shorter missions at the start of the year for training and to
 test systems. The longest missions in Aquarius are 14 days, but this doesn't happen too often. We are talking 
about a special project next year that might last 30 days. Interestingly, and this relates to the technique of 
saturation diving that we support, once you are saturated it doesn't matter if you stay 1 day, a week, or a 
month - the decompression time remains the same. A brief explanation of saturation diving is presented in the 
article: "How an Underwater Habitat Benefits Marine Science." Also, take a look at the pressure lesson plan to
 learn more about saturation diving. At the end of missions aquanauts decompress inside Aquarius, where 
pressure is slowly brought back to one atmosphere (or surface pressure) from the operating depth of about 
50 feet - and it takes over 17 hours. Aquanauts then "lock-out" and swim to the surface. People sometimes 
think that Aquarius is brought to the surface during decompression, but it stays on the bottom; it's the
 pressure inside Aquarius that is change.