The ass-kicking HMS Venturer
In February of 1945, the HMS Venturer encountered and trailed German U-Boat U-864 while submerged near Fedje, Norway. After a lengthy trail, the HMS Venturer decided to fire a spread of torpedoes at the submerged U-Boat in winch one of their four torpedoes struck home and sank the German sub. This action is the only known instance where a submerged sub sank another submerged sub and Capt. Launders' technique to plot a torpedo in a 3D environment is the bases of how its done to this day.
Give a cheer to some bad-ass Brits who mastered shooting torpedoes from the hip,