A small free-moving underwater vehicle designed by the Swiss-born professor Auguste Piccard (1884–1962), for exploring the ocean depths. His first two were balloon shaped and in the second he reached a depth of 4,050 metres (13,284 ft) in February 1954. With Italian assistance, he constructed a third, Trieste I, in which the balloon shape was abandoned for that of a cylindrical tank beneath which was a spherical observation chamber. In 1958 this was acquired by the US Navy and, after extensive reconstruction, touched bottom at 10,915 metres (35,812 ft) in the Marianas Trench on 25 January 1960.
Subjects: Warfare and Defence — Maritime History.