Deepest Ocean Dive
Jacques Piccard and Don Walsh descended to the deepest point in the ocean in bathyscaphe Trieste
January 23, 1960
Reaching the Bottom of the Sea
On January 23, 1960, U.S. Navy Lieutenant Don Walsh and Swiss oceanographer Jacques Piccard descended to the bottom of the Challenger Deep — the deepest known point in the ocean, located in the Mariana Trench in the western Pacific — aboard a vessel called the Trieste. They reached a depth of approximately 35,800 feet (about 10,900 meters), nearly seven miles below the surface. No one had ever gone that deep before, and no one would reach the same depth again for more than 50 years. The descent took nearly five hours. At the bottom, they observed a flatfish, shrimp, and other creatures, proving that life could exist even at the most extreme depths.
The Trieste and How It Worked
The Trieste was a bathyscaphe — a free-diving self-propelled deep-sea vessel. Unlike a submarine, which uses ballast tanks to control depth, the Trieste used a large float filled with gasoline (which is lighter than water) to provide buoyancy, and steel pellets as ballast to descend. The crew sat inside a small, thick steel sphere attached beneath the float. The pressure at the bottom of the Challenger Deep is about 1,000 times greater than at the surface — enough to crush a conventional submarine instantly. During the descent, one of the outer Plexiglas windows cracked, shaking the vessel, but the steel pressure sphere held and the crew were unharmed.
Exploring the Deep Ocean
The 1960 dive opened a new era of deep-sea exploration. In the decades since, unmanned submersibles have mapped large portions of the ocean floor, discovering hydrothermal vents teeming with unique life forms, vast underwater mountain ranges, and shipwrecks like the Titanic. In 2012, filmmaker James Cameron made a solo dive to the Challenger Deep in a specially designed submersible. In 2019, a submersible reached the bottom with explorer Victor Vescovo, who spent four hours on the bottom and found plastic waste there. The deep ocean remains the least explored part of our planet — vast, mysterious, and teeming with life we are only beginning to understand.