Nadia, Love of My Life - S1.E39

Shiki and the gang get through Dragonfall and arrive at the Aoi Cosmos, which is ruled by Poseidon Nero of the Oración Seis Galáctica, and land on a fire planet, Red Cave, at the suggestion of Witch. The planet is overflowing with Water Ether, and is an environment that is a far cry from a "fire planet" covered by the ocean. As the Edens Zero crew enjoy a brief vacation at the ocean, they discover a town beneath the waters...!