This is quite an anxious wartime drama that goes some way to illustrating the perils faced by those in HM Submarine Service. John Mills is the captain "Armstrong" who takes his crew on a routine maritime patrol only for their gear to become ensnared in a mine cable. A suddens stop and reverse engines doesn't quite do the trick and to the bottom they go. Largely in one piece and not in such deep water, they are optimistic of rescue and, indeed, help arrives fairly sharpish allowing the first four of the twelve survivors to don their emergency gear and head to the surface. The sense of enclosure ...