Deepest point in the sea

- Who
- Challenger Deep
- What
- 10,935 metre(s)
- Where
- Guam
- When
- 01 October 2010
The deepest point in the sea is the Challenger Deep, located beneath the Pacific Ocean about 300 km (186 mi) south-west of Guam. The maximum depth as measured by a crewed submersible that has travelled to and observed the seabed of the Challenger Deep is 10,935 m (35,876 ft), give or take 6 m (95% probability), based on data obtained across a series of dives to the "Eastern Pool" of the depression in June 2020. These dives were piloted by retired naval officer and explorer Victor Vescovo (USA) in the DSV Limiting Factor and the final depth was verified after analysis of the raw data by independent hydrographic experts, including ocean scientist/former NOAA administrator Dr Kathryn Sullivan who accompanied Vescovo on one of the dives.
In October 2010, the US Navy survey ship USNS Sumner measured the bottom of the Challenger Deep from the surface to be 10,994 m (36,070 ft) below sea level. Other surveys have measured roughly similar depths, with figures varying from 10,900 m (35,760 ft) (measured as part of the British Challenger II expedition in 1951) to 11,034 m (36,201 ft) (measured by the Soviet research ship Vityaz in 1957). But there is more room for error when measuring from the surface.
The Challenger Deep forms part of a large fault in the ocean floor called the Mariana Trench and was first discovered by the HMS Challenger – for which the feature is named – on 23 March 1875. The original depth soundings – done by lowering a weighted line into the sea – resulted in an estimated depth of 8,184 m (26,850 ft / 4,475 fathoms), which has been consistently revised down as measuring methods improve. Confusingly, the Royal Navy has had 8 ships called Challenger over the last 200 years, three of which were survey ships.
Vescovo had previously visited the Challenger Deep in April/May 2019 where over two dives he measured an average peak depth of 10,925 m (35,843 ft). His visit to the Challenger Deep marked the fourth leg on his Five Deeps Expedition, a mission to visit the deepest points in each of Earth's five oceans. He successfully completed the mission on 24 August 2019 after returning from the Molloy Deep, the deepest point in the Arctic Ocean.