Mexico, Gulf of, arm of the Atlantic Ocean, c.700,000 sq mi (1,813,000 sq km), SE North America. The Gulf stretches more than 1,100 mi (1,770 km) from west to east and c.800 mi (1,290 km) from north to south. It is bordered by the southeast coast of the United States from Florida to Texas, and the east coast of Mexico from Tamaulipas to Yucatán. Cuba is near the Gulf's entrance. On Cuba's northern side the Gulf is connected with the Atlantic Ocean by the Straits of Florida; on Cuba's southern side it is connected with the Caribbean Sea by the Yucatán Channel. Warm water from the Caribbean enters the Gulf through the Channel, forms a loop current off the U.S. and Mexican coasts, and then exits through the Straits as the Florida Current, becoming the Gulf Stream.
The Bay of Campeche (Bahía de Campeche), Mexico, and Apalachee Bay, Florida, are the Gulf's largest arms. Sigsbee Deep (12,714 ft/3,875 m), the Gulf's deepest part, lies off the Mexican coast. The shoreline is generally low, sandy, and marshy, with many lagoons and deltas. Chief of the many rivers entering the Gulf are the Mississippi, Alabama, Brazos, and Rio Grande. The U.S. Intracoastal Waterway follows the Gulf's northern coast.
Oil deposits from the continental shelf are tapped by offshore wells, especially near Texas and Louisiana. Most of the U.S. shrimp catch comes from the Gulf Coast; menhaden is also important. The discovery in the 1990s of a large oxygen-depleted "dead zone" off the Louisiana coast raised concerns about the effects of agricultural runoff on the Gulf; the zone has at times encompassed more than 8,000 sq mi (20,700 sq km). The chief Gulf ports are at Tampa and Pensacola, Fla.; Mobile, Ala.; New Orleans; Galveston and Corpus Christi, Tex.; Tampico and Veracruz, Mexico; and Havana, Cuba.