Some are clearly bad models on wires that don't move at all (Pterodactyl), some are puppets that rise from the water, whilst most are men in rubber suits lumbering around with some trulyawesome roaring monster sound effects.
Prometheus was some truly terrible sci - fi, and yet the adventures of Shaw and her unlikely companion, the «head - in - a-bag» David, could be hilariously awesome - sounds like a Heavy Metal story.