On 23 January 1960 the Navy's Bathyscaph Trieste dove to the deepest place in the world's oceans. This was the Challenger Deep in the Marianas Trench where the depth is 35,840 feet. I was
on board as the naval officer in command of the submersible along with Jacques Piccard of Switzerland, a consultant to our program.
The Trieste was the last of three bathyscaphs developed by Professor Auguste Piccard, a prominent Swiss physicist. Basically, bathyscaphs (literally "deep boats") were underwater free balloons with limited submerged mobility.
Piccard, assisted by his son Jacques, tested the first one in 1948. The second, was completed in 1953 and became the French Navy's FNRS-3. The Trieste, built in Italy in 1953 was the last.