Above Us The Waves, starring John Mills. 

John Mills is the gritty commander, tasked with the destruction of the German battleship Tirpitz. With the use of midget subs and a band of brave men he travels to Norway, to carry out the attack with the upmost daring do and stiff upperlipmanship (is that even a word?). Anyway, a cracking movie giving an insight to how brave these sailors were.