The New Adventures of Flash Gordon (1979)

Flash and Queen Fria cleverly gain entry in the lair of the eight-foot giants who have captured Dale and Dr. Zarkov. As Flash engages Brukka, Chief of the Giants, in a fight, Queen Fria frees the others from their ice pit prison cells. Flash and friends flee the caverns of the giants and gain their freedom by leaping to a swift river far below the giant stronghold. As the party rafts down the unknown river they encounter the horrifying spectacle of the glacier monster, a huge three-tentacled electrified river eel. Flash eventually short-circuits and destroys the glacier monster, gaining freedom at last. The party concludes its visit to Frigia as it boards a rocket railroad for the trip back to Arboria.