 Donald Walsh is stepping back in time at the National Museum of the United States Navy. Our job was to maintain and operate the bathyscaf. The scientists at the Navy lab would decide what kind of research projects we have and what kind of equipment we put on it to make measurements and sampling under the sea. In 1960, Mr. Walsh was a young Navy lieutenant. He co-piloted a free diving vehicle called the Trieste to the deepest part of the Pacific Ocean. What better demonstration of safety of this platform than to go to the deepest place in the ocean and come back and perfectly intact and in a working order. Mr. Walsh says the Trieste looks a little like a submarine. Basically it is an underwater balloon. You've got two parts to it. You've got the balloon here, which is this long cylindrical object, and that's filled with a lighter-than-water substance, which is aviation gasoline. Oil floats on water, so you get buoyancy or lift. And then beneath the balloon, like a balloon up in the air, you have a cabin for the fragile humans. There was just enough room for two people. Mr. Walsh and Swiss scientist Jacques Picard. On January 23, 1960, the Trieste began its historic dive. Nine and a half kilometers down, the two men heard something unusual. We got our attention, but we didn't know at the time what it was. We just knew they were still alive and everything was functioning well. All our instruments, indicators said that the dive was progressing just fine. The sound came from a crack forming in the window. Luckily, it did not leak, and the Trieste arrived in one piece at the deepest point of the Mariana Trench. Until recently, no one had returned to that part of the ocean. In March, filmmaker and explorer James Cameron reached the Mariana Trench alone in a vessel he designed. We know very little about the species that live down there. We know very little about the distribution of the biological communities. We don't know how these animals have adapted to living under this unbelievable pressure that exists down there. Mr Cameron's dive owes much to the dive a half century before by the crew of the Trieste. I'm Shirley Griffith.