From: USFW, 1982
Mississippi Sound extends from Lake Borgne, Louisiana to Mobile Bay, Alabama, spanning the entire Gulf coast of the state of Mississippi. The Sound is separated from the Gulf of Mexico by a series of narrow islands and sand bars including Cat, Ship, Horn, Petit Bois and Dauphin islands. Water exchange with the Gulf takes place through numerous passes. Numerous coastal bays are contained within the system including St. Louis Bay, Biloxi Bay, Pascagoula Bay and Grand Bay. The Escatawpa, Pascagoula, Tchoutacabouffa, Biloxi, Wolf and Jourdan Rivers (east to west) provide freshwater to the estuary.
The Mississippi Department of Natural Resources maintains over 20 marine reserves in the area, and the protected areas of these islands form a portion of the Gulf Islands National Seashore (see link below).