Overview: In 1969 off the California coast, a US Navy crane carefully lowered a massive tubular structure into the waters.

It was designed for an elite group of divers to spend days or even months at a stretch living and working on the ocean floor.

'American Experience: Sealab' tells the little-known story of the daring program that tested the limits of human endurance and revolutionized undersea exploration.

DVD Verdict: On a February day in 1969, off the shore of northern California, a US Navy crane carefully lowered 300 tons of metal into the Pacific Ocean.

The massive tubular structure was an audacious feat of engineering - a pressurized underwater habitat, complete with science labs and living quarters for an elite group of divers who hoped to spend days or even months at a stretch living and working on the ocean floor.

The Sealab I project, as it was known, was the brainchild of a country doctor turned naval pioneer who dreamed of pushing the limits of ocean exploration the same way NASA was pushing the limits of space exploration.

As Americans were becoming entranced with the effort to land a man on the moon, these divers, including one of NASA's most famous astronauts, were breaking depth barrier records underwater.

Watching this really quite fascinating hour long PBS program we quickly learn that not everything was about Sealab I itself.

Before the Sealab I habitat could be emplaced, a number of rifle grenades had to be found and removed from the bottom around Argus Island!

The grenades had been fired up into the air with the object of targeting their explosions when they returned to the water.

With enough impacts the position of Argus Island could be determined to within a few feet.

Unfortunately, many grenades did not detonate upon impact with the sea surface, and divers had to locate and remove them. This was a job for divers from the Navy SOFAR Station (Columbia University Geophysical Field Station), and both U.S. Navy and Air Force civilians and enlisted SCUBA divers.

A platform that had been built to lower the Remote Underwater Manipulator (RUM) from a garage on Argus Island to the sea floor was also removed. Sealab I was then placed on the nearly flat bottom on a layer of algal balls and some corals.

Sealab I was commanded by Captain George F. Bond, also called "Papa Topside", who was key in developing theories about saturation diving.

The project proved that saturation diving in the open ocean was viable for extended periods. The experiment also offered information about habitat placement, habitat umbilicals, humidity, and helium speech descrambling.

Sealab I is on display at the Museum of Man in the Sea, in Panama City Beach, Florida, near where it was initially tested offshore before being deployed.

It is on outdoor display. Its metal hull is largely intact, though the paint faded to a brick red over the years. However, the habitat's exterior was restored as part of its 50th year anniversary, and now sports its original colors. This is a Widescreen Presentation (1.85:1) enhanced for 16x9 TVs.