This is the final installment in Universal's uneven "Gill Man trilogy," which began with Creature from the Black Lagoon and was followed by Revenge of the Creature, is the least interesting of the bunch. The story finds the prehistoric amphibian far from his Amazon home, kept under close scientific scrutiny in a special facility in Florida. After a laboratory fire severely damages the creature's gills, the head of the research team (Jeff Morrow) initiates an operation that will allow their subject to breathe through a set of latent lungs. After some attempts are made to acclimate the creature to life among human beings, Morrow's plans are destroyed by his own pettiness when one of his colleagues (Gregg Palmer) makes romantic overtures toward his wife, leading to a violent confrontation that leaves the creature badly injured. Alone in alien territory, the Gill Man resolutely shuffles off into the sea -- presumably to commit suicide, since he no longer possesses the ability to breathe underwater. This disappointing conclusion to the series makes little use of the 3-D thrills that enlivened the original and forsakes the opportunity to present a literal fish-out-of-water story in favor of hackneyed melodrama. Champion diver Ricou Browning again portrays the creature in the underwater sequences, with Don Megowan donning the gill-less Gill Man suit on land.
by Cavett Binion synopsis