What primary feature characterizes a lagoon?

A lagoon is primarily characterized by its isolation from the ocean. This isolation can be due to various natural features such as sandbars, barrier islands, or coral reefs that separate the lagoon from the open sea. The resulting shallow water body often maintains distinct ecological conditions, including different salinity levels, depths, and water temperatures compared to the adjacent ocean.

While lagoons can have variations in salinity, the defining characteristic is their relative seclusion, allowing for unique habitats and ecosystems to develop. The other choices do not accurately represent what fundamentally defines a lagoon. Multiple rivers flowing into a body of water, high salinity levels, or freshwater influx can occur in various water bodies but do not specifically characterize a lagoon itself.