The depression is named after the British Royal Navy survey ship , whose expedition of 1872–1876 made the first recordings of its depth. The high water pressure at this depth makes designing and operating exploratory craft difficult. The first descent by any vehicle was by the manned bathyscaphe "Trieste" in January 1960; unmanned visits followed in 1996, 1998 and 2009. In March 2012 a manned solo descent was made by film director James Cameron in the deep-submergence vehicle "Deepsea Challenger". Between 28 April and 4 May 2019, the "DSV Limiting Factor" completed four manned dives to the bottom of Challenger Deep. Between 6 June and 26 June 2020, the "DSV Limiting Factor" added six completed dives. Between 1 March and 11 March 2021, the "DSV Limiting Factor" added four completed dives. As of March 2021 the list of people who descended to Challenger Deep comprises seventeen people.