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

Henry A. Escalante

Chico

Ricou Browning

The Gill Man In Water (uncredited)

Art Gilmore

Narrator (voice) (uncredited)

Perry Lopez

Tomas (uncredited)

Sydney Mason

Dr. Matos (uncredited)

Rodd Redwing

Luis (uncredited)

James Miller

Old Man (uncredited)

Ben Chapman

The Gill Man On Land (uncredited)