The film was a monumental flop in its day no doubt because, rather mysteriously with such much at stake, the opportunity to alter history and all that, so little happens. Somehow, with every build-up to action someone decides that it is probably not a good idea and everything comes to nothing. But this mood of recurring suspension is the film's charm. It is rare for Americans to actually reflect on their situation rather than blow something to kingdom come Even this however would not be enough were not the film sustained by a high level of technical accuracy (it was clearly shot with generous Navy co-operation). It is precisely when the film tries to imbue proceedings with dramatic interest that it shows its B-grade Twilight Zone credentials (not surprisingly director Taylor spent most of his career, before and after this, in television), notably with the tacked-on ending which attempts to tie the two time frames together but which does not even remotely convince.
The Final Countdown is an oddball film made in Hollywood's pre-Bruckheimer days (and with no sign of that dreadful Europe song of the same name which would be a chart topper six years later).