Are You Afraid of the Dark?

S04:E05 - The Tale of the Water Demons

Shawn and Dean are entranced by an old sea captain's tales of diving deep sea wrecks for treasure. But the captain is plagued by water demons--the ghosts of the victims of the wrecks--that visit him every time he dozes off and won't let him rest. To lift the curse from the Captain, Shawn and Dean set out to get all his salvaged treasure back to the bottom of the ocean--but come face to face with the water demons themselves.