Odin-class submarine
The "Odin"-class submarine (or "O class") was a class of nine submarines developed and built for the Royal Navy (RN) in the 1920s. The prototype, , was followed by two boats originally ordered for the Royal Australian Navy, but transferred to the RN in 1931 because of the poor economic situation in Australia, and six modified boats ordered for the RN. Three modified boats were built for the Chilean Navy as the s in 1929. Design. The class was built to replace the ageing L-class submarines which did not have adequate endurance for use in the Pacific  Ocean. These boats were theoretically able to dive to , though none were formally tested beyond . Armament consisted of eight torpedo tubes (6 bow, 2 stern) and one gun. The boats were of a saddle tank type with fuel carried in riveted external tanks. These external tanks proved vulnerable to leaking after depth charge damage, thus betraying the position of the submarine. These boats were the first British submarines fitted with Asdic and VLF radio which could be used at periscope depth.