Following a U-boat attack, those who remain seize control of the submarine after it surfaces for battery recharging. An initial understanding between the two crews quickly falls apart, leading them to unexpectedly emerge in a prehistoric landscape populated by dinosaurs and early humans. The film hinges on whether they manage to return home, a question left to Doug McClure and John McEnery, whose performances are somewhat stiff but enjoyable. Considering the resources available, the creatures and visual effects are adequate, although occasional glimpses of rigging are noticeable. As with other viewers who experienced this movie during their childhood, I find myself remembering it fondly, perhaps more so than its production quality warrants. Nevertheless, it provides a pleasant escapade and remains worth seeing.

Source on TMDB