What do you call a body of water that is separated from larger bodies of water by a natural barrier?

A lagoon is characterized as a body of water that is typically separated from a larger body of water, such as an ocean or a sea, by a natural barrier such as a sandbar, coral reef, or barrier island. This separation creates a distinct ecosystem within the lagoon that can have different salinity levels and water characteristics compared to the connected larger body of water. The presence of these natural barriers allows lagoons to form calm waters that often host a variety of marine life, making them important for biodiversity.

In contrast, a bay is a body of water partially enclosed by land, but it is not necessarily separated by a barrier in the same way lagoons are. A sea is a larger body of saltwater that is connected to other oceans or bodies of water, while an inlet refers to a narrow body of water between land, leading into a larger body of water, but does not imply the same separation achieved by lagoons. Thus, the definition of a lagoon highlights the unique aspect of being separated by a natural barrier, solidifying its distinction from the other options.