Don Walsh

Don Walsh was a young US Navy officer with a submarine background when the Navy purchased the bathyscaphe Trieste, a deep-diving submersible designed by the Piccard family, and assigned him to help operate it as part of a research programme into the deep ocean. He worked alongside Jacques Piccard, whose father had designed the vessel, learning its unfamiliar controls and the specific dangers of operating a small crew sphere under pressures no vehicle had previously survived.

On 23 January 1960 the two men descended into the Challenger Deep, the deepest known point of the Mariana Trench, in a dive lasting roughly five hours down and another three hours back up. Partway through the descent a window pane in the outer hull cracked audibly, a moment Walsh later described as genuinely frightening, since a full failure at that depth would have been unsurvivable. They continued anyway and reached a depth of around 10,916 metres, still the deepest point any crewed vehicle would reach for more than fifty years afterward.

Walsh left active naval service in 1975 and became a professor of ocean engineering, spending the following decades as one of the most respected figures in oceanography, consulted on deep submersible design and safety by later generations of ocean explorers, including the team behind Victor Vescovo's Five Deeps Expedition and film-maker James Cameron's solo dive to the same trench in 2012.

He continued working and advising into his nineties, widely regarded as a mentor figure across the field he had helped establish. He died in 2023 at the age of ninety-two.