Sediments color Lagoa dos Patos (English: Duck Lagoon), tan and frame the nearby Brazilian coastline. Lagoa dos Patos is the second largest lagoon in Latin America and the biggest in Brazil. It is located in the state of Rio Grande do Sul, southern Brazil. The lagoon is 174 miles (280 km) long, has a maximum width of 44 miles (70 km), and a total area of 3,803 sq. mi. (9,850 km). It is separated from the Atlantic Ocean by a sandbar about 5 miles (8 kilometers) wide. The Rio Grande, at the south end of Lagoa dos Patos, forms the outlet to the Atlantic. 
According to the Ramsar Convention for the conservation and sustainable utilization of wetlands, recognizing the fundamental ecological functions of wetlands and their economic, cultural, scientific, and recreational value is internationally important.
Lagoa do Peixe National Park is 34,4000 hectares and is made up of the Campos Sulinos (Southern Fields) and Mata Atlântica (Atlantic Rain Forest) biomes. It includes representative samples of the ecosystems of the Rio Grande do Sul coastal zone such as saltmarsh, coastal dunes and lagoons, arboreal habitat, restingas, beach and a marine area. The beauty of the park's dunes and lagoons can be appreciated by all park visitors. Lagoa do Peixe National Park was named after the lagoon found within the reserve with the same name. Lagoa do Peixe is the largest lagoon within the park; it is shallow and is about 35 km long, making it an important feeding ground for birds.
