 Gene EvansSteve Karnes | Steve Karnes |
 André MorellProf. James Bickford | Prof. James Bickford |
 Leigh MadisonJean Trevethan | Jean Trevethan |
 John TurnerJohn | John |
 Alastair HunterDr. C. A. Morris, the village doctor | Dr. C. A. Morris, the village doctor |
 Lloyd LambleSenior Admiral, at the Admiralty | Senior Admiral, at the Admiralty |
 Jack MacGowranDr. Sampson, the paleontologist | Dr. Sampson, the paleontologist |
 Maurice KaufmannMini Submarine Officer | Mini Submarine Officer |
 Henri VidonTom Trevethan | Tom Trevethan |
 Patrick JordanPhoto Lab Aide | Photo Lab Aide |
| HHoward LangNaval Commader, at the "Valkyrie" wreck (uncredited) | Naval Commader, at the "Valkyrie" wreck (uncredited) |
 Leonard SachsDialogue Scientist at Conference (bit) | Dialogue Scientist at Conference (bit) |
| EErnest BlythScientist at Conference (uncredited) | Scientist at Conference (uncredited) |
| NNeal ArdenTV Newscaster (uncredited) | TV Newscaster (uncredited) |
| PPaul BeradiMan Listening to Car Radio (uncredited) | Man Listening to Car Radio (uncredited) |
 Max FaulknerPLA Radio Operator (uncredited) | PLA Radio Operator (uncredited) |
 Neil HallettDr. Sampson's Helicopter Pilot (uncredited) | Dr. Sampson's Helicopter Pilot (uncredited) |
 André MaranneFrench Radio Officer (uncredited) | French Radio Officer (uncredited) |
 Derren NesbittThe Radar Operator, at the radar room (uncredited) | The Radar Operator, at the radar room (uncredited) |
 Guy StandevenNaval Officer in Situation Room (uncredited) | Naval Officer in Situation Room (uncredited) |
