 | Peter Weller als Steven Beck |
 | Richard Crenna als Dr. Glen 'Doc' Thompson |
 | Amanda Pays als Elizabeth 'Willie' Williams |
 | Daniel Stern als Buzz 'Sixpack' Parrish |
 | Ernie Hudson als Justin Jones |
 | Michael Carmine als Tony 'DeJesus' Rodero |
 | Lisa Eilbacher als Bridget Bowman |
 | Hector Elizondo als C.P. Cobb |
 | Meg Foster als Ms. Martin |
 | Eugene Lipinski als Russian Ship Captain |
 | Larry Dolgin als Helicopter Pilot |
 | Pascal Druant als Winch Operator |
| Steve Pelot als Winch Operator |
 | Tom Woodruff Jr. als Lead Creature (uncredited) |
| George P. Cosmatos | Director |
| David Webb Peoples | Story |
| David Webb Peoples | Screenplay |
| Jeb Stuart | Screenplay |
| Aurelio De Laurentiis | Producer |
| Luigi De Laurentiis | Producer |
| Charles Gordon | Executive Producer |
| Lawrence Gordon | Executive Producer |
| Jerry Goldsmith | Original Music Composer |
| Alex Thomson | Director of Photography |
| John F. Burnett | Editor |
| Roberto Silvi | Editor |
| Jane Feinberg | Casting |
| Mike Fenton | Casting |
| Lynda Gordon | Casting |
| Ron Cobb | Production Design |
| Franco Ceraolo | Art Direction |
| Pier Luigi Basile | Supervising Art Director |
| David F. Klassen | Art Direction |
| William Ladd Skinner | Supervising Art Director |
| Bruno Cesari | Set Decoration |
| Robert Gould | Set Decoration |
| April Ferry | Costume Design |
| Giorgio De Vincenzo | Post Production Supervisor |
| Lucio Trentini | Production Supervisor |
| Maria Teresa Barbasso | Set Designer |
| Marco Trentini | Set Designer |
| Roberto Malerba | Location Manager |
| Ceri Evans | Script Supervisor |
| Gabriella Toro | Production Coordinator |
| Robin Gregory | Sound Mixer |
| Jon Curtis Price | Creature Design |
| Nancy Beach | Orchestrator |
| Jerry Goldsmith | Conductor |
| Kenneth Hall | Supervising Music Editor |
| Arthur Morton | Orchestrator |
| Michael Dittrick | Music Editor |
| Gillian L. Hutshing | Assistant Editor |
| Richard Leeman | First Assistant Editor |
| Aldo Manni | Negative Cutter |
| Augusto Grassi | Costumer |
| Yvonne Zarb Cousin | Costumer |
| Ramón Bravo | Underwater Camera |
| Phil Barthropp | Underwater Camera |
| Tony Cridlin | Grip |
| Federico Del Zoppo | Additional Photography |
| Giuseppe Maccari | Cinematography |
| Ernesto Natoli | Assistant Camera |
| Fabio Scepi | Electrician |
| Mike Valentine | Underwater Camera |
| Bruce Barlow | Special Effects Makeup Artist |
| Katalin Elek | Makeup Artist |
| Zoltan Elek | Key Makeup Artist |
| Marina Marin | Assistant Hairstylist |
| John Rosengrant | Special Effects Makeup Artist |
| Aldo Signoretti | Key Hair Stylist |
| Marco Alberti | Second Second Assistant Director |
| Matt Earl Beesley | First Assistant Director |
| Luca Lachin | Second Assistant Director |
| Kuki López Rodero | First Assistant Director |
| David Turchi | Second Assistant Director |
