Lake Maracaibo (Spanish: Lago de Maracaibo) is a large brackish bay in Venezuela at 10°39′N 71°36′W. It is connected to the Gulf of Venezuela by Tablazo Strait (55km) at the northern end, and fed by numerous rivers, the largest being the Catatumbo. It is commonly considered a lake rather than a bay or lagoon, and at 13,210 km² it would be the largest lake in South America. The geological record shows that it has been a true lake in the past, and as such is one of the oldest lakes on Earth at 20-36 million years old.
Lake Maracaibo acts as a major shipping route to the ports of Maracaibo and Cabimas. The surrounding Maracaibo Basin contains large reserves of crude oil, making the lake a major profit center for Venezuela. A dredged channel gives oceangoing vessels access to the bay. Wikipedia