Ben Gazzara as Cmdr. Adrian Blake

Walter Pidgeon as Dr. Samuel Andrews

Ernest Borgnine as Chief Diver Don MacKay

Yvette Mimieux as Dr. Leah Jansen

Donnelly Rhodes as Diver Bob Cousins

Chris Wiggins as Capt. Williams

Mark Walker as Diver Dave Moulton

Leslie Carlson as Brigs, Triton Radioman

Stuart Gillard as Diver Phil Bradley

Michael J. Reynolds as Dr. Hal Hamilton

Kay Fujiwara as Anita, lab technician