The British U-class submarines were a class of 49 small submarines built just before and during the Second World War. The class is sometimes known as the Undine class, after the first submarine built. A further development was the British V-class submarine of 1942.
HMS Salmon was a second-batch S-class submarine built during the 1930s for the Royal Navy. Completed in 1935, the boat fought in the Second World War. Salmon is one of twelve boats named in the song "Twelve Little S-Boats".
The Capitan O'Brien class were three submarines built for the Chilean Navy in the late 1920s. Designed and built in the United Kingdom, they were a modified design of the contemporary British Odin-class submarines. The lead boat, Capitan O'Brien, was launched on 2 October 1928 and the other two on 15 January 1929. All three submarines entered service in 1929. The three vessels remained in service until being discarded in 1957–1958.
HMS L2 was a L-class submarine built for the Royal Navy during World War I.
HMS Saga was a S-class submarine of the third batch built for the Royal Navy during World War II. She survived the war and was sold to Portugal.
HMS Selene was a S-class submarine of the third batch built for the Royal Navy during World War II. She survived the war and was sold for scrap in 1961.
HMS Seneschal was a S-class submarine of the third batch built for the Royal Navy during World War II. She survived the war and was sold for scrap in 1965.
HMS Sentinel was a S-class submarine of the third batch built for the Royal Navy during World War II. She was not completed until after the war and was sold for scrap in 1962.
HMS Surf was a S-class submarine of the third batch built for the Royal Navy during World War II. She survived the war and was scrapped in 1948.
HMS Spur was a S-class submarine of the third batch built for the Royal Navy during World War II. She survived the war and was sold to Portugal in 1948.
HMS Spearhead was a S-class submarine of the third batch built for the Royal Navy during World War II. She survived the war and was sold to Portugal. She was scrapped in 1967.
HMS Supreme was a S-class submarine of the third batch built for the Royal Navy during World War II. She survived the war and was sold for scrap in 1950.
HMS Spark was a S-class submarine of the third batch built for the Royal Navy during World War II. She survived the war and was scrapped in 1950.
HMS Stoic was a S-class submarine of the third batch built for the Royal Navy during World War II. She survived the war and was scrapped in 1950.
HMS Subtle was a S-class submarine of the third batch built for the Royal Navy during World War II. She survived the war and was scrapped in 1959.
HMS Sterlet was a second-batch S-class submarine built during the 1930s for the Royal Navy. Completed in 1938, the boat fought in the Second World War. The submarine is one of the 12 boats named in the song Twelve Little S-Boats. Thus far she has been the only ship of the Royal Navy to be named Sterlet.
HMS Snapper was a second-batch S-class submarine built during the 1930s for the Royal Navy. Completed in 1935, the boat participated in the Second World War. Snapper is one of the 12 boats named in the song "Twelve Little S-Boats".
HMS Sealion was a second-batch S-class submarine built during the 1930s for the Royal Navy. Completed in 1934, the boat fought in the Second World War.
HMS Seawolf was a second-batch S-class submarine built during the 1930s for the Royal Navy. Completed in 1936, the boat fought in the Second World War.
HMS Oberon was the prototype for the Odin-class submarine of the Royal Navy.
