- Bill Baldwin - Patrol Boat Dispatcher (voice / uncredited)
- Jere Beery - Photographer (uncredited)
- Ricou Browning - The Gill Man (in water) / Lab Technician (uncredited)
- Diane DeLaire - Miss Abbott (uncredited)
- Mike Doyle - Cop (uncredited)
- Clint Eastwood - Jennings (uncredited)
- Jack Gargan - Skipper (uncredited)
- Charles Gibb - Cop (uncredited)
- Brett Halsey - Pete (uncredited)
- Don C. Harvey - Mac - Spotlight Party Leader (uncredited)
- Tom Hennesy - The Gill Man (on land) / Marineland Diver (uncredited)
- Don House - Diver (uncredited)
- Robert F. Hoy - Charlie (uncredited)
- Ned Le Fevre - Newscaster (uncredited)
- Sydney Mason - Police Announcer (uncredited)
- Robert Nelson - Dr. McCuller (uncredited)
- Patricia Powers - Girl in Convertible
- Bert Stevens - Search Party Member (uncredited)
- Charles Victor - Policeman (uncredited)
- Robert Wehling - Joe (uncredited)
- James R. Wolfe - Man at Tank (uncredited)
- Jack Arnold
- Fred Frank
- William Alland
- William Alland
- Henry Mancini
- Leslie I. Carey
- Hans J. Salter
- William Lava
- Milton Rosen
- Herman Stein
John Agar interpreta a Prof. Clete Ferguson en la película.
Lori Nelson hace el papel de Helen Dobson.
John Bromfield interpreta a Joe Hayes en la película.
Nestor Paiva interpreta a Captain Lucas en la película.
Grandon Rhodes hace el papel de Jackson Foster.
Dave Willock hace el papel de Lou Gibson.
Robert B. Williams interpreta a George Johnson en la película.
Charles Cane hace el papel de Police Captain.
Loretta Agar interpreta a Woman on Boat (uncredited) en la película.
Bill Baldwin interpreta a Patrol Boat Dispatcher (voice / uncredited) en la película.
Jere Beery hace el papel de Photographer (uncredited).
Ricou Browning interpreta a The Gill Man (in water) / Lab Technician (uncredited) en la película.
Diane DeLaire interpreta a Miss Abbott (uncredited) en la película.
Mike Doyle interpreta a Cop (uncredited) en la película.
Clint Eastwood hace el papel de Jennings (uncredited).
Jack Gargan interpreta a Skipper (uncredited) en la película.
Charles Gibb interpreta a Cop (uncredited) en la película.
Brett Halsey hace el papel de Pete (uncredited).
Don C. Harvey hace el papel de Mac - Spotlight Party Leader (uncredited).
Tom Hennesy interpreta a The Gill Man (on land) / Marineland Diver (uncredited) en la película.
Don House interpreta a Diver (uncredited) en la película.
Robert F. Hoy interpreta a Charlie (uncredited) en la película.
Ned Le Fevre interpreta a Newscaster (uncredited) en la película.
Sydney Mason hace el papel de Police Announcer (uncredited).
Robert Nelson interpreta a Dr. McCuller (uncredited) en la película.
Patricia Powers interpreta a Girl in Convertible en la película.
Bert Stevens hace el papel de Search Party Member (uncredited).
Charles Victor hace el papel de Policeman (uncredited).
Robert Wehling hace el papel de Joe (uncredited).
James R. Wolfe interpreta a Man at Tank (uncredited) en la película.
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