Jellyfishs are first seen, when Fujimoto pour his elixir into water. Ponyo take the chance to leave her home. Then outside she eats a jellyfish. She swims away and lays on a jellyfish, who floats to the top of the ocean. She take a smaller jellyfish to cover her body on the travel. Ponyo on a jellyfish is a common display cover for the movie.
Near the end of the movie Granmamare calls a giant jellyfish to cover the kindergarten and the nursing home for the elderly.