Ep 3. Island of the Body Snatchers

When Thundarr, Ariel and Ookla investigate an island where there have been a number of unexplained shipwrecks, the find the lair of the sorceress Circe -- who has been cursed to turn to stone if she leaves her island. To escape, she must find a young sorceress whom she can trick into swapping bodies, a sorceress like Ariel!