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.
Deep-sea exploration
In general, modern scientific Deep-sea exploration can be said to have begun when French scientist Pierre Simon de Laplace investigated the average depth of the Atlantic ocean by observing tidal motions registered on Brazilian and African coasts. He calculated the depth to be , a value later proven quite accurate by soundings measurement. Later on, with increasing demand for submarine cables installment, accurate soundings was required and the first investigations of the sea bottom were undertaken. The first deep-sea life forms were discovered in 1864 when Norwegian researchers obtained a sample of a stalked crinoid at a depth of . The British Government sent out the "Challenger" expedition (a ship called ) in 1872 which discovered 715 new genera and 4,417 new species of marine organisms over the space of four years.