The highest point that science has been able to bring mankind to so far is atomic power, and that has been used to create the most advanced form of propulsion in the atomic submarine, such as the one which Commander Pete Mathews (Kenneth Tobey) is in charge of. All seems to be running smoothly until the radar picks up a strange shape coming towards them from the depths of the sea; at first they cannot believe something that huge could be anything but a malfunction in the equipment - that is when suddenly the shape catches up with the sub.
This was the beginning of one of the most fruitful partnerships in special effects cinema, as it marked the first film where the team of producer Charles H. Schneer and the legendary stop-motion maestro Ray Harryhausen collaborated. In truth it was so low budget that the much-anticipated monster, the one which came from beneath the sea, only appeared twice in the first hour for about a minute each time, and as was an eighty-minute movie they were not exactly generous with their action sequences. Therefore the bulk of this took up the relationship between Pete, regulation beautiful lady scientist Lesley (Faith Domergue) and stuffy scientist John (Donald Curtis).
So while you were awaiting the grand finale you could muse over gender politics in sci-fi flicks of the fifties as Pete makes a play for Lesley, but finds John interested in her too. They don't exactly pursue her aggressively, but the film doesn't appear to be too clear whether they think she should be bothering her pretty little head about all this science business or be settling down with one or other of her suitors. The scream she gives out when she claps eyes on the monster for the first time suggests Domergue's role was not as forward-thinking as you might have hoped, but you took what you could get for advances in gender equality in movies such as these, and Lesley was no doormat otherwise.
Besides, they needed the romantic angle to beef up the plot, which aside from the presence of the monster was rather underfed otherwise. The main source of fear we were supposed to be experiencing with regard to the creature was that no matter how our technology had travelled, there was still the worry that someone - or in this case something - would be able to beat us at our own game. Often in this type of fiction that would be a metaphor for the Communists on the other side of the world, but here it seemed to be more Mother Nature that represented the threat, at least as far as the monster being radioactive went, because they usually were radioactive in these movies, weren't they?
The beast itself was a rampant octopus, which famously had six arms instead of eight for budgetary reasons, not that you'd really notice unless it was pointed out to you (as, er, it often was), and it was big enough to take down the Golden Gate Bridge should it be thus inclined - and it was. It was the final fifteen minutes which made up for the previous, rather facile run up to the showdown between the Navy and the monster, as it flung its tentacles around San Francisco and smashed up buildings and squashed fleeing citizens as Pete and his cohorts try to put their love lives behind them for the moment and work out a way of stopping it before it destroys everything in its path. Even at this relatively early stage in his career, Harryhausen was displaying a mastery of his medium, and the giant abomination giving the human cast such a headache was a highly amusing creation. The rest was a bit of a trial.