Humans first descended into Challenger Deep in 1960 using a U.S. Navy submersible.
Notes on verification
Confirmed by multiple independent, authoritative sources including AAAS, USNI, and Wikipedia. Minor simplification: Piccard was a civilian Swiss engineer, not U.S. Navy personnel, though the vessel was U.S. Navy-operated and Walsh was Navy.
Sources
- The Pacific Ocean—facts and information (nationalgeographic.com)
- https://www.aaas.org/membership/scientia/back-challenger-deep (aaas.org)
- https://www.usni.org/magazines/proceedings/2020/january/first-deepest-dive (usni.org)