4. The bathysphere was built by Americans William Beebe and Otis Barton. On 11 June 1931 they used it to descend 900 m off the coast of Bermuda.
5.
6. The first bathyscaphe, the FN RS 2, was developed by Swiss scientist August Piccard between 1946 and 1948. An improved version, the FNRS 3, descended 4000 m off Senegal on 15 February 1954.