 "Salmon" is one of twelve boats named in the song "Twelve Little S-Boats".On 4 December 1939, "Salmon" became the first boat to sink a U-boat during the Second World War when it torpedoed and sank the German in the North Sea south-west of Kristiansand, Norway.The second batch of S-class submarines were designed as slightly improved and enlarged versions of the earlier boats of the class and were intended to operate in the North and Baltic Seas.