As the torpedo left a Swordfish or Albacore, a tension wire unreeled from the aircraft and controlled its entry attitude. Fins and the wire made the weapon belly-flop into the water instead of diving steeply. The wire then detached once it had done its work. The resulting shallow run let the torpedo clear the harbor bottom and strike ships where a conventional drop might bury it in the mud. A later Pearl Harbor comparison says Japanese torpedoes received extra fins but lacked the British tension-wire method, and some ran into the harbor mud.
Notable Point · 3:49:59-3:50:55
The tension wire behind shallow-water torpedo attacks
A tension wire and stabilizing fins made British aerial torpedoes belly-flop rather than dive deeply, enabling the shallow-water attack at Taranto.