Submarine and diving bell, 1929. Diving bell and submarine docked in a harbour. This set-up was used at Key West, Florida, USA, in salvage tests on the USS S-4 (SS-109). The conical fitting on the bottom of the diving bell was shaped to fit the submarine's hatch. The USS S-4 (SS-109) was an S-class submarine of the United States Navy. She sunk on 17 December 1927 in an accidental ramming by a Coast Guard destroyer, with the loss of the entire crew. The vessel was raised in March 1928 and restored to service in October 1928. It was decommissioned in 1933 and finally stricken (and sunk) in 1936. Photographed in December 1929.