Having placed mines on the hull of a British warship whilst it is safe in harbour during the second World War , the two man crew of an Italian miniature submarine are captured and held prisoner whist the crew try and discover the nature of their mission! Written by
Did You Know?
The events seen in the film are based on a true story of an attack by Italian 'human torpedoes' which successfully blew up both the "Queen Elizabeth" and the "Valiant" on 18th December 1941. The real Bianchi was not shot but lost his grip on the torpedo when it dived, making it impossible for his commander De La Pene on his own to attach the machine physically to the ship's hull as they had intended. (He later explained that his refusal to talk had been because the British could have saved their ship very simply if they had realized the true nature of the 'mine', which was simply lying on the bottom of the harbor) The two men were imprisoned in the bottom of the warship as depicted here, and finally five minutes before the explosion was due De la Pene sent a warning to Captain Morgan enabling him to muster the crew safely on the top deck (although not to abandon ship). Neither of the Italians was injured in the explosion. The British really did successfully conceal from Italian espionage the damage to both warships for months. See more
In the film, the Italians are seen to be given away by the bubbles rising from their breathing apparatus; during the war, the Italian frogmen used pure oxygen 'pendulum' breathing sets, in which exhaled gas is returned to the tank via a carbon dioxide filter, rather than the compressed-air apparatus used in peacetime - precisely in order to avoid the problem of a tell-tale string of bubbles. See more