Prof. Clete Ferguson

John Agar

Acting

Helen Dobson

Lori Nelson

Acting

Joe Hayes

John Bromfield

Acting

Captain Lucas

Nestor Paiva

Acting

Jackson Foster

Grandon Rhodes

Acting

Lou Gibson

Dave Willock

Acting

George Johnson

Robert B. Williams

Acting

Police Captain

Charles Cane

Acting

Woman on Boat (uncredited)

Loretta Agar

Acting

Patrol Boat Dispatcher (voice / uncredited)

Bill Baldwin

Acting

Photographer (uncredited)

Jere Beery

Acting

The Gill Man (in water) / Lab Technician (uncredited)

Ricou Browning

Acting

Miss Abbott (uncredited)

Diane DeLaire

Acting

Cop (uncredited)

Mike Doyle

Acting

Jennings (uncredited)

Clint Eastwood

Acting

Skipper (uncredited)

Jack Gargan

Acting

Cop (uncredited)

Charles Gibb

Acting

Pete (uncredited)

Brett Halsey

Acting

Mac - Spotlight Party Leader (uncredited)

Don C. Harvey

Acting

The Gill Man (on land) / Marineland Diver (uncredited)

Tom Hennesy

Acting

Diver (uncredited)

Don House

Acting

Charlie (uncredited)

Robert F. Hoy

Acting

Newscaster (uncredited)

Ned Le Fevre

Acting

Police Announcer (uncredited)

Sydney Mason

Acting

Dr. McCuller (uncredited)

Robert Nelson

Art

Girl in Convertible

Patricia Powers

Acting

Search Party Member (uncredited)

Bert Stevens

Acting

Policeman (uncredited)

Charles Victor

Acting

Joe (uncredited)

Robert Wehling

Acting

Man at Tank (uncredited)

James R. Wolfe

Crew