Troy falls asleep, whilst on stand by duty, and dreams of a meeting between him and a group of undersea cavemen who have found the cargo of a crashed ship, the Shenandoah, a vessel which was carrying radioactive material.
| Actor | Role |
|---|---|
 Don MasonCaptain Troy Tempest (voice) | Captain Troy Tempest (voice) |
 Robert EastonLieutenant George Lee 'Phones' Sheridan (voice) | Lieutenant George Lee 'Phones' Sheridan (voice) |
 Ray BarrettCommander Sam Shore / Sub-Lieutenant John Horatio Fisher (voice) | Commander Sam Shore / Sub-Lieutenant John Horatio Fisher (voice) |
 Lois MaxwellLieutenant Atlanta Shore (voice) | Lieutenant Atlanta Shore (voice) |
 David GrahamOld Caveman / Caveman 1 / Caveman 2 (voice) | Old Caveman / Caveman 1 / Caveman 2 (voice) |