Stingray (1964)

S1E9 Raptures of the Deep

The Stingray crew embarks on a mission to save two reckless treasure hunters. During the operation, Troy accidentally tumbles into a deep crevasse, leading to a critical shortage of air that causes him to lose consciousness. Upon awakening, he realizes he can breathe effortlessly without any equipment and has unexpectedly become the wealthiest person on the planet.