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.
Hadal zone
James Cameron also reached the bottom of Mariana Trench in March 2012 using the "Deepsea Challenger". The descent of the "Deepsea Challenger" was unable to break the deepest dive record set by Piccard and Walsh by about 100 meters, however Cameron holds the record for the deepest solo dive.