Trieste is a Swiss-designed, Italian-built deep-diving research bathyscaphe. In 1960, it became the first crewed vessel to reach the bottom of Challenger Deep in the Mariana Trench, the deepest point in Earth's seabed. The mission was the final goal for Project Nekton, a series of dives conducted by the United States Navy in the Pacific Ocean near Guam. The vessel was piloted by Swiss oceanographer Jacques Piccard and US Navy lieutenant Don Walsh. They reached a depth of about 10,916 metres (35,814 ft).
Trieste shortly after her purchase by the US Navy in 1958
Pressure sphere, with forward ballast hopper, left
Don Walsh and Jacques Piccard aboard Trieste
Trieste just before the Mariana dive 23 January 1960, seen escorted by USS Lewis
A bathyscaphe is a free-diving, self-propelled deep-sea submersible, consisting of a crew cabin similar to a Bathysphere, but suspended below a float rather than from a surface cable, as in the classic Bathysphere design.
Bathyscaphe Trieste before its only dive into the Mariana Trench
The Trieste in 1958