An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries, located at the boundary of marine and freshwater ecosystems, form a transition zone between river environments and ocean environments. Estuaries vary in shape and size ranging from coastal embayments and drowned river valleys, to coastal lakes and smaller intermittently open and closed lagoons (ICOLLS). Estuaries offer immense value from an ecological, social and economic perspective. Estuarine foreshores are desirable places on which to live and work and their waterways are popular for a wide variety of active and passive recreational pursuits.

There are three estuaries within Byron Shire: Brunswick Estuary, Tallow Creek and Belongil Creek.