<P> The extreme conditions in the deep sea require elaborate methods and technologies, which has been the main reason why its exploration has a comparatively short history . In the following, important key stones of deep sea exploration are listed . </P> <Ul> <Li> 1521: Ferdinand Magellan tried to measure the depth of the Pacific Ocean with a 2,400 ft (732 m) weighted line, but did not find bottom . </Li> <Li> 1818: The British researcher Sir John Ross was the first to find that the deep sea is inhabited by life when catching jellyfish and worms in about 2,000 m (6,562 ft) depth with a special device . </Li> <Li> 1843: Nevertheless, Edward Forbes claimed that diversity of life in the deep sea is little and decreases with increasing depth . He stated that there could be no life in waters deeper than 550 m (1,804 ft), the so - called Abyssus theory . </Li> <Li> 1850: Near the Lofoten, Michael Sars found a rich deep sea fauna in a depth of 800 m (2,625 ft) thereby refuting the Abyssus Theory . </Li> <Li> 1872--1876: The first systematic deep sea exploration was conducted by the Challenger expedition on board the ship HMS Challenger led by Charles Wyville Thomson . This expedition revealed that the deep sea harbours a diverse, specialized biota . </Li> <Li> 1890--1898: First Austrian - Hungarian deep sea expedition on board the ship SMS Pola led by Franz Steindachner in the eastern Mediterranean and the Red Sea . </Li> <Li> 1898--1899: First German deep sea expedition on board the ship Valdivia led by Carl Chun; found many new species from depths greater than 4,000 m (13,123 ft) in the southern Atlantic Ocean . </Li> <Li> 1930: William Beebe and Otis Barton are the first humans to reach the Deep Sea when diving in the so - called Bathysphere, made from steel . They reach a depth of 435 m (1,427 ft), where they observed jellyfish and shrimp . </Li> <Li> 1934: The Bathysphere reached a depth of 923 m (3,028 ft). </Li> <Li> 1948: Otis Barton set out for a new record reaching a depth of 1,370 m (4,495 ft). </Li> <Li> 1960: Jacques Piccard and Don Walsh reached the bottom of the Challenger Deep in the Mariana Trench, descending to a depth of 10,740 m (35,236 ft) in their deep sea vessel Trieste, where they observed fish and other deep sea organisms . </Li> <Li> 2012: The vessel Deepsea Challenger, piloted by James Cameron, completes the second manned voyage and first solo mission to the bottom of the Challenger Deep . </Li> </Ul> <Li> 1521: Ferdinand Magellan tried to measure the depth of the Pacific Ocean with a 2,400 ft (732 m) weighted line, but did not find bottom . </Li> <Li> 1818: The British researcher Sir John Ross was the first to find that the deep sea is inhabited by life when catching jellyfish and worms in about 2,000 m (6,562 ft) depth with a special device . </Li>

Who conducted the first acoustical exploration of the seas