evidence: Although it is a well-watered land, no large rivers flow entirely within Uruguay. The Uruguay River and the estuary of the Río de la Plata, along the western border of the nation, are navigable for oceangoing ships until Paysandú and for smaller vessels above that point to the falls at Salto. The smaller Negro River, which traverses the country from northeast to southwest, is navigable only in its lower part, below Rincón del Bonete Lake (the Río Negro Reservoir). Among other small rivers are the Santa Lucía, Cebollatí, and Queguay Grande. Merín (Mirim) Lagoon, which lies mainly within Brazil, is the largest natural lake.