The U.S. state of Texas has a series of estuaries along its coast on the Gulf of Mexico, most of them bounded by the Texas barrier islands. Estuaries are coastal bodies of water in which freshwater from rivers mixes with saltwater from the sea. Twenty-one drainage basins terminate along the Texas coastline, forming a chain of seven major and five minor estuaries: listed from southwest to northeast, these are the Rio Grande Estuary, Laguna Madre, the Nueces Estuary (Corpus Christi Bay), the Mission–Aransas Estuary (Aransas Bay), the Guadalupe Estuary (San Antonio Bay), the Colorado–Lavaca Estuary (Matagorda Bay), East Matagorda Bay, the San Bernard River and Estuary, the Brazos River Estuary, Christmas Bay, the Trinity–San Jacinto Estuary (Galveston Bay), and the Sabine–Neches Estuary (Sab