Richard Carlson

Dr. David Reed

Julie Adams

Kay Lawrence

Richard Denning

Dr. Mark Williams

Antonio Moreno

Dr. Carl Maia

Nestor Paiva

Captain Lucas

Whit Bissell

Dr. Edwin Thompson

Bernie Gozier

Zee

Ricou Browning

The Gill Man In Water (uncredited)

Art Gilmore

Narrator (voice) (uncredited)

Perry Lopez

Tomas (uncredited)

Rodd Redwing

Luis (uncredited)

Ben Chapman

The Gill Man On Land (uncredited)