I think you may be referring to the WWII Italian submersible teams that initially had great success blowing up British ships by sneaking up on them in a harbor and attaching explosives to the hull. The History Channel made it out like this was such a revolutionary idea. What the History Channel seemed to forget, was that we (the Americans) first used the concept during the Revolutionary War with a spherical submarine made of wood named, "Turtle." The link below has a good desciption.