Oceanid is a water-world dimension where there's no land mass on the entire planet.
Aquaman's wife Mera and their son A.J. lived there together in peace until the planet was devastated by alien invasion. They were attacked by a far-trawling race called the Maritorn led by the despotic Lord Nemo. Aquaman was called in to help protect their world. Using Naiad to help him connect with the entire world's oceans, he coordinated a counter-attack with the Oceanids against the invaders that quickly devastated their fleet in a single strike. In the aftermath, Aquaman and Mera returned to their home dimension, while A.J. became the new Aquaman of his.
- A.J. and Mera were originally sent to Oceanid by accident using a portal.