Terrible science (e.g. sinking ice) and terrible plot and dialogue but the magnificent Seaview saves the film. It was the sub which went on to star in the popular TV series in the next decade, a series which had that famous theme music.
In in the right mood this is an enjoyable film. Watch the secretary, Barbara Eden, totter around the deck in high heels taking shorthand at every opportunity
It is the opposite of everything they put on the enveloppe to advertise the film. It is sooo predictable, so corny! Of course one can say it is dated but there are many films in those days that were much better science fiction than that. People in a submarine (it looks like a sardine tin) are pretty scared by ridiculous events; even these great movie stars could not save the film, in fact the film 'drown' them.