Rio de la Plata
The Río de la Plata (River of Silver) is usually rendered River Plate in British English and the Commonwealth, and occasionally rendered [La] Plata River in other English-speaking countries — is the estuary formed by the confluence of the Uruguay River and the Paraná River on the border between Argentina and Uruguay. It is a funnel-shaped indentation on the southeastern coastline of South America, about 290 km (180 mi) long. The Río de la Plata widens from about 2 kilometres (1.2 mi) at the inner part to about 220 kilometres (140 mi) at its mouth. It forms part of the border between Argentina and Uruguay, with the major ports and capital cities of Buenos Aires and Montevideo on its western and northern shores, respectively. The coasts of the Río de la Plata are the most densely populated areas of Argentina and Uruguay.
The Río de la Plata includes the La Plata dolphin or Franciscana (Pontoporia blainvillei) which is found in coastal Atlantic waters of southeastern South America. It is a member of the river dolphin group and the only one that actually lives in the ocean and saltwater estuaries, rather than inhabiting exclusively freshwater systems.