American scientists get more than they bargained for on an expedition when a dark tributary turns up a prehistoric man with gills. The creature breaks free after being captured, menacing the adventurers and stealing away the only woman on the crew.

• 1 hr 20 min
• Directed by

  Jack Arnold
• Written by Harry J. Essex, Arthur A. Ross

• Starring

  Richard Carlson

  ,

  Julie Adams

  ,

  Richard Denning

  ,

  Antonio Moreno

  ,

  Nestor Paiva

  ,

  Whit Bissell

  ,

  Bernie Gozier

  ,

  Henry Escalante

  ,

  Julio Lopez

  ,

  Sydney Mason

  ,

  Rodd Redwing