One of the craziest but successful ideas was the magnetic noisemaker. The Canadians came up with it to drop on the Soviet subs. Once the magnets got into all the nooks and crannies, the sub would have to go to dry dock and spend countless hours removing panels etc., to get all the buggers. Worth a laugh!
The magnets worked on the Soviets with maddening results. The crews of several Foxtrots were driven bonkers by the noise and returned to port rather than complete their cruises.
http://nationalinterest.org/blog/the...omb-them-21477