The New Adventures of Flash Gordon (1979)

Fleeing from Princess Aura's robot rocket attack, Flash Gordon and his friends are attacked by a mysterious magnetic ray as they fly over the sea of mystery. Flash's rocket ship crashes and he, Dale and Dr. Zarkov are pulled beneath the sea into the multi-spired undersea city of Coralia. There Queen Undina has special machine altering techniques applied to Flash and his friends so they can breathe water as easily as they did air. Flash and Dr. Zarkov help Coralia Queen Undina defeat Ming's underwater laser firing submarine attack. Queen Undina rewards them with restoration of their air breathing ability and freedom, and as the chapter ends the group heads for Arboria.