A pretty unremarkable John Wayne movie about dud torpedoes. Varied quality miniature effects, most close ups suffering from poor depth of focus. Many shots taken from much earlier films and exhibiting an obvious grainy quality. A particularly odd over use of a totally out of focus miniature periscope shot. Some shots appear to have been shot out at sea rather than in a tank as the horizon and sky look real. Some of the underwater tank work, particularly the violence of the depth charges is well done while a few of the shots which I suspect were lifted from earlier films suffer from the overly clear pool water and obvious pool sides in the background. Amusingly the sub sailors in the film are watching a sub movie complete with miniature shots of a submarine.