At the start of World War II, "Sturgeon" conducted patrols in the North Sea. On 6 September, she was mistakenly bombed by British aircraft. On her second patrol, she fired three torpedoes at an unidentified submarine, which was in fact her sister ship , but the torpedoes missed. On her third patrol, she missed the German U-boat and was damaged after hitting the bottom, requiring repairs. On 20 November, she sank the German armed trawler with torpedoes. The sinking was the first successful attack by a British submarine of the war, and was a morale boost for British submariners. During her next patrols in the North Sea, "Sturgeon" sighted and sank several ships, including the German troop transport "Pionier" and the Danish merchants SS "Sigrun" and SS "Delfinus". Afterwards, "Sturgeon" patrolled in the Bay of Biscay, acted as a beacon during Operation Torch, then, after being again damaged by Allied aircraft, escorted the Arctic Convoys PQ 15 and PQ 17. "Sturgeon" was transferred to the 8th Submarine Flotilla, which operated on the Mediterranean Sea, in October 1942 to support the Allied landings in North Africa. In May 1943, she was loaned to the Royal Netherlands Navy as HNLMS "Zeehond". "Zeehond" was returned to the Royal Navy following the war and was sold for scrap in 1946. She was one of the four submarines that formed the First Group of the S class, and the only one of these to survive the war.