They were significantly taller than humans, having the head, body and texture of a shark, very sharp teeth, clawed fins, and webbed feet. They were cunning, ravenous, and ferocious, attacking and feeding on anything that crossed their path. Although their steel-like skin made them invulnerable to conventional weapons, they could be killed by either long periods out of salt water or prolonged, high-pitched noise, after which their flesh disintegrated, leaving behind their vertebrae.