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.
DeepFlight Challenger
It was planned that Branson would pilot the sub to the Puerto Rico Trench, while Chris Welsh would pilot it for the Mariana Trench dive. Virgin Oceanic had hoped to be the first team to solo to the bottom of the Mariana Trench, and first team to return to the Challenger Deep since the Bathyscaphe Trieste, the first submersible to dive to the Challenger Deep, left, however, James Cameron's Deepsea Challenge project beat them to it in March 2012. There has been an undeclared race on to return to the Challenger Deep between four teams, Cameron's, Virgin Oceanic's, Google-Schmidt/DOER's, and Triton Submarines'. The attempt on Challenger Deep had been announced in April 2011.