Aerial torpedo experts in all modern navies had previously thought that torpedo attacks against ships must be in water at least deep. Taranto harbour had a depth of only about ; but the Royal Navy had developed a new method of preventing torpedoes from diving too deep. A drum was attached beneath the nose of the aircraft, from which a roll of wire led to the nose of the torpedo. As it dropped, the tension from the wire pulled up the nose of the torpedo, producing a belly-flop rather than a nose dive.