The Plane of Water
The Elemental Plane of Water, or Vatnaheim, is an endless ocean. There are settlements here which lie on the shallower parts of the seabed. Coral reefs, kelp forests, and deep ravines hold many dangers. Chief among them is Jormungandr, the World Serpent, who will come to Midgard during Ragnarok and devour all life in the oceans.