<P> Only four descents have ever been achieved . The first descent by any vehicle was by the manned bathyscaphe Trieste in 1960 . This was followed by the unmanned ROVs Kaikō in 1995 and Nereus in 2009 . In March 2012 a manned solo descent was made by the deep - submergence vehicle Deepsea Challenger . These expeditions measured very similar depths of 10,898 to 10,916 metres (35,755 to 35,814 ft). </P> <P> Over many years, the search for the point of maximum depth has involved many different vessels . </P> <Ul> <Li> The HMS Challenger expedition (December 1872--May 1876) first sounded the depths now known as the Challenger Deep . This first sounding was made on 23 March 1875 at station 225 . The reported depth was 4,475 fathoms (26,850 ft; 8,184 m) at 11 ° 24 ′ N 143 ° 16 ′ E ﻿ / ﻿ 11.400 ° N 143.267 ° E ﻿ / 11.400; 143.267, based on two separate soundings . </Li> <Li> A 1912 book, The Depths of the Ocean by Sir John Murray, records the depth of the Challenger Deep as 31,614 ft (9,636 m), reporting the sounding taken by the converted navy collier USS Nero in 1899 . Murray was one of the expedition scientists . </Li> <Li> In 1951, about 75 years after its original discovery, the entire Mariana Trench was surveyed by a second Royal Navy vessel, captained by George Stephen Ritchie (later Rear Admiral Ritchie); this vessel was also named HMS Challenger, after the original expedition ship . This survey recorded the deepest part of the trench using echo sounding, a more precise and easier way to measure depth than the sounding equipment and drag lines used in the original expedition . A depth of 5,960 fathoms (35,760 ft; 10,900 m) was measured at 11 ° 19 ′ N 142 ° 15 ′ E ﻿ / ﻿ 11.317 ° N 142.250 ° E ﻿ / 11.317; 142.250 . </Li> </Ul> <Li> The HMS Challenger expedition (December 1872--May 1876) first sounded the depths now known as the Challenger Deep . This first sounding was made on 23 March 1875 at station 225 . The reported depth was 4,475 fathoms (26,850 ft; 8,184 m) at 11 ° 24 ′ N 143 ° 16 ′ E ﻿ / ﻿ 11.400 ° N 143.267 ° E ﻿ / 11.400; 143.267, based on two separate soundings . </Li>

Who has gone the deepest in the ocean