Mary Allen
Marine animals include all animal species that live mainly in the sea. So there are fish, starfish, crabs, mussels, jellyfish, sponges, and many more. Many seabirds, especially penguins, but also sea turtles live mostly in or near the sea, but lay their eggs on land. Seal mothers give birth to their young on land. All these animals are still considered marine animals.
The theory of evolution assumes that all original animals lived in the sea. Many then went ashore and developed further there. But there are also animals that later migrated back to the sea after moving from sea to land: the ancestors of whales and bony fish lived on land and only later migrated to the sea. So these are also counted among the sea creatures.
It is therefore not entirely clear which animals belong to the sea creatures since they are not related in terms of evolution. This is similar to the forest animals. It also depends a lot on which sea it is. Near the equator, the water is warmer than in the Arctic or Antarctica. That is why other marine animals also live there.