Near the river's mouth, the Senegal goes through Biffeche and there is an island in the river. The city of Saint-Louis is on this island. The river then turns south. There is a thin line of sand and this separates the river from the Atlantic Ocean. The line of sand is called the Langue de Barbarie. After this, the river enters the Atlantic Ocean. The river has two large dams: the Manantali Dam in Mali, and the Maka-Diama Dam on the Mauritania-Senegal border, near the sea. The Manantali Dam makes a reservoir. The Maka-Diama Dam stops salt water going deep into the countryside.