Estuaries are areas where freshwater meets saltwater referred to as brackish water.
The estuary includes the arm of the sea such as a sound or bay that extends inshore to merge with the river mouth. The St. Simons and Jekyll Island Sounds receive water from several rivers and creeks. Habitats that are part of the estuary may include the salt marsh, mud or tidal flats, sounds, and tidal creeks. These environments include the most biologically productive ecosystems in nature. E stuaries are rich because they are great absorbers and trap nutrients that flow into them.