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.
Kaikō ROV
In March 1995, "Kaikō" became the second vessel ever to reach the bottom of the Challenger Deep, and the first craft to visit this location since the "Trieste" mission. The maximum depth measured on that dive was 10,911.4 meters, marking the deepest dive for an unmanned submersible to date. On 31 May 2009, "Nereus" became the third vessel to visit the bottom of the Challenger Deep, reaching a maximum recorded depth of 10,902 meters.