Stingray (1964)

S01E18 The Cool Cave Man

As Troy contemplates his attire for a high-class costume ball in Atlanta, he dozes off and envisions a thrilling showdown with a tribe of submerged cavemen who are stealing cargo from a ship carrying radioactive substances. After awakening from this wild dream, Troy is motivated to don a caveman costume for the event—much to his surprise, he discovers that everyone else has decided to join in on the prehistoric theme as well!