Routine and quite boring 1960s war film concentrating on the X-series of midget submarines. In this typical afternoon matinee movie James Caan appears as a totally miserable and humourless Canadian submarine commander. Presumably Caan appears to make the film saleable in North America. The underwater scenes and onshore action don't add up to much but the occasional glimpses of scenery around the Scottish lochs makes marginally for some of the tedium. The shoot out with German paratroopers has some tension and excitement. Overall, one for rainy, cold, wintery Sunday afternoons. 3/10.