Galveston Bay is mostly shallow with an average depth of 7–9 feet. It is fed by the Trinity River and the San Jacinto River, numerous local bayous and incoming tides from the Gulf of Mexico. This unique and complex mixing of waters from different sources supports many types of marine life including crabs, shrimp, oysters, and many varieties of fish thereby supporting a substantial fishing industry. Additionally the system of bayous, rivers, and marshes that ring the Bay support their own ecosystems allowing for diverse wildlife and enabling freshwater farming of crawfish. The areas near the bay shore in fact have a higher diversity of habitats than the nearby Gulf coast.