The Coatzacoalcos is a large river that feeds mainly the south part of the state of Veracruz; it originates in the Sierra de Niltepec and crosses the state of Oaxaca in the region of the Isthmus of Tehuantepec, flowing for 325 kilometres (202 miles)[1][2] toward the Gulf of Mexico.

[3]: 34  Hernán Cortés sent Diego de Ordaz to explore the river as a possible port.

[4] According to legend, the Mesoamerican god Quetzalcoatl was aboard a raft made of a serpent skin and navigated until getting lost into the horizon.

The Coatzacoalcos is also among the world's most contaminated rivers, partly because of the lack of environmental laws protecting the public water.

[6] According to the Mexican Center of Environmental Law (CEMDA) the biggest polluting body is the petrochemical industry of Mexico Pemex.