Struggling against capturing a a dangerous creature, a group of scientists head to the Amazonian jungle. Things come to challenge them, as they fight for their life.
Jack Arnold has a flair for this sort of thing, and if there really is anything frightening about a man dressed up in a rubber suit with zippers where the gills ought to be, Arnold comes close to finding it.
The underwater sequences were excellently shot by Havens, and the make-up for the half man, half fish was a masterful creation by Bud Westmore and Jack Keven.
