The Movie Insider.com

The story involves the members of a fossil-hunting expedition down a dark tributary of the mist-shrouded Amazon, where they enter the domain of a prehistoric, amphibious "Gill Man" — possibly the last of a species of fanged, clawed humanoids who may have evolved entirely underwater. Tranquilized, captured and brought aboard, the creature still manages to revive and escape — slaughtering several members of the team — and abducts their sole female member, spiriting her off to his mist-shrouded lair. This sparks the surviving crewmen to action — particularly those who fancy carrying the girl off themselves.