Bradford Dillman as Paul Grogan

Heather Menzies as Maggie McKeown

Kevin McCarthy as Dr. Robert Hoak

Keenan Wynn as Jack

Dick Miller as Buck Gardner

Barbara Steele as Dr. Mengers

Belinda Balaski as Betsy

Melody Thomas Scott as Laura Dickinson

Bruce Gordon as Colonel Waxman

Barry Brown as Trooper

Paul Bartel as Mr. Dumont

Shannon Collins as Suzie Grogan

Shawn Nelson as Whitney

Richard Deacon as Earl Lyon

Janie Squire as Barbara Randolph

Roger Richman as David

Bill Smillie as Jailer

Guich Koock as TV Pitchman

Jack Pauleson as Boy in Canoe

Eric Henshaw as Father in Canoe

Robert Vinson as Soldier

Virginia Dunnam as Girl

Diamond Farnsworth as Water-skier

Bruce Paul Barbour as Man in Boat

Robyn Ray as Screaming Woman

Mike Sullivan as Dam Guard

Jack Cardwell as Brandy

Sally Bondi as Swimming Deb (uncredited)

Eric Braeden as Dr. Robert Hoak (swimming double) (uncredited)

Joe Dante as Scuba Diver #2 (uncredited)

Amy Holden Jones as Hertz Clerk (uncredited)

Andrew G. La Marca as Scuba Diver #1 (uncredited)

John Sayles as Army Sentry (uncredited)

Phil Tippett as Scuba Diver (uncredited)