Torpedoes could be, and were, used against dams. On the 2nd February 1941, the Royal Navy carried out Operation Picket. This was an attack on the Santa Chiara d’Ula dam on the Tirso River on the Italian island of Sardinia. Eight torpedo-carrying Fairey Swordfish strike aircraft were launched from HMS Ark Royal on the 2nd February. Bad weather split the attacking force, and the aircraft attacked independently. The first aircraft to attack encountered heavy AA fire, causing its pilot to jettison his torpedo and abandon the attack. The next two aircraft came in from a different angle, avoiding the worst of the AA batteries. They successfully dropped their torpedoes. A fourth aircraft made a low-level approach and attack following the river. This approach meant that the aircraft took no fire until it climbed after dropping its torpedo. The last two aircraft to attack encountered heavy cloud over the target; one became lost, jettisoned its torpedo and headed home, while the other managed to make an attack. The final aircraft of the eight was shot down before it could attack, with its crew surviving to become prisoners. Four torpedoes were dropped against the dam, yet little damage was done.

The failure of Operation Picket points out part of the reason why torpedoes were not used for Operation Chastise, the more famous 'Dambusters' raid. RAF experts calculated that it would take a total of ~20,000 lbs of explosives detonated close to the face of a dam to destroy it. The standard British aerial torpedo of the early war, the Mk XII, had a 388 lb warhead, while the later Mk XV had a 545 lb warhead. 'Upkeep', the famous bouncing bomb, had a warhead of a little under 3,000 lb. In other words, you would need fewer aircraft successfully attacking the target with a bouncing bomb than with torpedoes, increasing the chances of success. There were other issues, too. The dams were protected with torpedo nets. These were large, thick nets (originally developed to protect battleships in harbour) that could catch or divert torpedoes. A bouncing bomb could make its way over the nets and to the target, while a torpedo would be stopped. Upkeep was also designed to place its explosives directly against the dam face, at a depth chosen to maximise the effect of the blast. Torpedoes had difficulty with depth-keeping, and could not be relied upon to do this.

Torpedoes were, however, successfully used against a dam in Korea. US Navy aircraft attacked the Hwacheon Dam in May 1951. The dam had been captured by Chinese and North Korean forces, who were releasing water from it to hamper UN operations downstream. Eight torpedo aircraft attacked the dam, with seven scoring hits. However, the aim of this raid was different from that of Operations Picket or Chastise. The USN was not seeking to destroy the dam. Instead, they were looking to knock out the sluice gates that controlled the level of water in the dam. By destroying the gates, they limited the amount of control that the Communist forces had. One gate was destroyed completely, another holed, and several more damaged.