It was back on October 3 that the two professors from Roane State Community College in Tennessee donned their scuba gear and descended toward an underwater laboratory in a bay off the coral reef island of Key Largo in Florida.

The laboratory they entered at a depth of 7 meters (25 feet) can only be accessed by divers. Once inside, they dried themselves, put on fresh clothes and made themselves at home.

In the chamber, the atmospheric pressure was a constant 26 psi (1.8 bar), just less than double the pressure at sea level.

For what is in essence is a large dive bell, the laboratory was equipped unusually comfortably, with several beds, a small kitchenette and a refrigerator. Its glass windows provide a view of the coral reefs. An opening in the bottom allowed divers to continually resupply the two with fresh food, drinks - albeit, non-alcoholic - and clothing. They even had a TV and wireless Internet.

Pumps delivered fresh air through a hose.

Even pizza was delivered here - in waterproof packaging

Learning from professionals

Previously, the record for an uninterrupted stay in such a diving bell was 69 days. Fain and Cantrell broke had already broken that record by Thursday (December 11).

Medically, theirs was a case of "saturation diving," a method often used by professionals who have to work under pressure for extended periods of time. It is also often found with workers doing construction work in "caissons" - sealed underwater structures that are under pressure, for example, when building tunnels or bridge foundations.

Caissons allow workers to stay under pressure for extended periods of time, thus avoiding the medically risky procedure of going back and forth between the different pressure environments

Few dangers

Unlike for scuba divers, nitrogen posed few problems for the professors. At depths of 25 feet, the effects of nitrogen narcosis - when divers become euphoric, lose focus and fail to realize what's happening around them - are non-existent. Typically narcosis sets in at depths of 70 to 90 feet.

Decompression sickness, which can lead to lung blockages and fatal heart attacks, was similarly hypothetical at a depth of 25 feet. Once the two professors reached maximum saturation, nitrogen levels held steady. When leaving the diving bell and resurfacing, they simply had to follow standard surfacing procedure from a depth of 25 feet. Had they ascended too quickly, nitrogen that had previously dissolved in the blood would not have been able to traverse the circulatory system fast enough to be exhaled.

No boredom allowed

The accomplishment of the two record holders, therefore, is not so much one of scuba medicine but one of psychological endurance. Spending two month in a metal barrel under water requires strong nerves.

But the two had a good share of distractions: They could receive guests in the laboratory and were linked to the outside world through intercom, the Internet and a telephone. They also spent time answering letters from interested elementary and high-school students.

Fain and Cantrell also gave weekly lectures via the Internet. They received Halloween candy and even made a short horror film while under water.

The high point of their stay was a visit by American astronaut Buzz Aldrin - the second man on the moon after Neill Armstrong