It's a Lagoon.
A lagoon is a shallow body of water that features an opening to the ocean or larger body of water. A lagoon is often separated from these larger bodies of water by barrier islands or reefs.
This sounds very much like a Lagoon. Also a Fjordcould possibly fit this definition although they tend to be long and narrow and quite a bit deeper than a Lagoon.
they live in the ocean
A ocean wave changes when it reaches the shallow water because it washes away the land which is not onshore.
Shallow parts of the sea or ocean are called shoals or shallows. They are areas where the water depth is relatively shallow, making them potentially hazardous for navigation.
neritic
because it is warmer
DEEP!
A protected area inland of a sandbar is known as a lagoon. Lagoons are shallow bodies of water separated from a larger body of water, like an ocean, by a sandbar or barrier island. They provide habitat for various species of plants and animals and are often used for recreational activities.
Well shallow water means that it is not deep so i would think that it means like walking around in a shallow pool or ocean. That's just my guess.
A body of water that is protected from the ocean by an arm of land is called a harbor. You will often find harbors within a gulf or in a bay.