Bathyscaphe Trieste
On 23 January 1960, she reached the ocean floor in the Challenger Deep (the deepest southern part of the Mariana Trench), carrying Jacques Piccard and Don Walsh. This was the first time a vessel, manned or unmanned, had reached the deepest known point of the Earth's oceans. The onboard systems indicated a depth of , although this was revised later to ; fairly recently, more accurate measurements have found Challenger Deep to be between and deep.
Challenger Deep
The 2009 and 2010 maximal depths were not confirmed by the series of dives "Nereus" made to the bottom during an expedition in May–June 2009. The direct descent measurements by the four expeditions which have reported from the bottom, have fixed depths in a narrow range from () to (), to ("Nereus") to () Although an attempt was made to correlate locations, it could not be absolutely certain that "Nereus" (or the other descents) reached exactly the same points found to be maximally deep by the sonar/echo sounders of previous mapping expeditions, even though one of these echo soundings was made by "Nereus" mothership.