A body of water such as you describe would be the ocean itself.
Coast A relatively small area of water would be called a bay, and a larger area of water would be called a gulf.
That is a peninsula.
A body of water that is partially enclosed by land is called a bay. Sometimes this type of water body can be referred to as an inlet as well.
Peninsulas typically have three sides surrounded by water, as they are partially connected to a larger landmass by a narrow strip or isthmus.
Land that is nearly surrounded by water is called a peninsula.
a bay
A shoreline indentation is called a bay. It is a curved area of water partially surrounded by land, often less exposed to the open sea than a gulf.
An area of land completely surrounded by water is called an island.
When an object is immersed in water, it means it is completely surrounded or covered by the water.
== == A Bay
An island is a piece of land entirely surrounded by water.