Richard Carlson
Dr. David Reed
Acting
Julie Adams
Kay Lawrence
Acting
Richard Denning
Dr. Mark Williams
Acting
Antonio Moreno
Dr. Carl Maia
Acting
Nestor Paiva
Captain Lucas
Acting
Whit Bissell
Dr. Edwin Thompson
Acting
Bernie Gozier
Zee
Acting
Henry A. Escalante
Chico
Acting
Ricou Browning
The Gill Man In Water (uncredited)
Acting
Art Gilmore
Narrator (voice) (uncredited)
Acting
Perry Lopez
Tomas (uncredited)
Acting
Sydney Mason
Dr. Matos (uncredited)
Acting
Rodd Redwing
Luis (uncredited)
Acting
James Miller
Old Man (uncredited)
Acting
Ben Chapman
The Gill Man On Land (uncredited)
Acting