Lt. Cmdr. John 'Twill' Twillinger

Gail MacKenzie

Dr. Jess Rogers

Jody Simms

Dr. Tad Johns

Lt. Robert 'Clem' Clemens

Sheriff Josh Peters

Sandy MacKenzie

Connie Blake

Seaman Fred Johnson

Sally

George Blake (lab assistant)

Mrs. Simms

Lewis Clark Dobbs

Seaman Wyatt (Radioman)

Seaman Morty Beatty

Monster Victim

Deputy Larry

Admiral Greenhouse

Deputy Scotty

Other Lock Watchman

Boy with Morty's Cap

Coroner Nate Brown

Gatekeeper

Patterson

Watchman at Lock 57

Seaman Howard Sanders

Davis - Resort Owner

Captain Masters

Deputy Brewer

Clarke

Story

Director

Conductor

Production Assistant

Sound Recordist

Sound Recordist

Producer

Screenplay

Casting

Special Effects

Director of Photography

Art Direction

Producer

Editor

Original Music Composer

Set Decoration

Other

Hairstylist

Other

Wardrobe Supervisor

Technical Supervisor

Other

Underwater Director of Photography

Makeup Artist

Music Director

Sound Mixer

Assistant Director

Other

Sound Recordist