what are some characteristics of an estuary
(Photo: Elkhorn Slough NERRS site). An estuary is a partially enclosed body of water, and its surrounding coastal habitats, where saltwater from the ocean mixes with fresh water from rivers or streams. In fresh water the concentration of salts, or salinity, is nearly zero.The salinity of water in the ocean averages about 35 parts per thousand (ppt).ruly, no two estuaries are the same. Yet they are typically classified based on two characteristics: their geology and how saltwater and fresh water mix in them. However, not all estuaries contain brackish waters. There are a small number of ecosystems classified as freshwater estuaries.