In a tributary of the Amazon, a monster – half-man, half-fish – is captured and placed in a reservoir in a Florida national park to be observed by scientists.
| Writing | Martin Berkeley | Screenplay |
| Directing | Jack Arnold | Director |
| Writing | William Alland | Story |
| Visual Effects | Jack Kevan | Creature Design |
| Camera | Scotty Welbourne | Director of Photography |
| Editing | Paul Weatherwax | Editor |
| Art | Alexander Golitzen | Art Direction |
| Art | Alfred Sweeney | Art Direction |
| Art | Russell A. Gausman | Set Decoration |
| Sound | William Lava | Original Music Composer |
| Art | Julia Heron | Set Decoration |
| Production | William Alland | Producer |
| Sound | Herman Stein | Original Music Composer |
| Costume & Make-Up | Bud Westmore | Makeup Artist |
| Sound | Jack A. Bolger, Jr. | Sound |
| Sound | Leslie I. Carey | Sound |
| Sound | Ben Hendricks | Sound Editor |
| Sound | Albert E. Kennedy | Sound Editor |
| Costume & Make-Up | Jay A. Morley Jr. | Costume Designer |
| Costume & Make-Up | Joan St. Oegger | Hairstylist |
| Production | Edward Dodds | Unit Production Manager |
| Directing | Fred Frank | Assistant Director |
| Crew | Tom Hennesy | Stunts |
| Crew | Don House | Stunts |
| Crew | Bob Hoy | Stunts |
| Crew | Ginger Stanley | Stunts |
| Sound | Joseph Gershenson | Music Supervisor |
| Sound | Henry Mancini | Music |
| Sound | Milton Rosen | Music |
| Sound | Ethmer Roten | Musician |
| Sound | Hans J. Salter | Music |
| Sound | Frank Skinner | Music |
