Rio Sucuriju is a tributary of the Rio Preguiças drainage system, flowing through the remarkable landscape of the Parque Nacional dos Lençóis Maranhenses in Maranhão, Brazil. Situated near the town of Barreirinhas, this river winds through one of Brazil's most visually stunning protected areas — a national park defined by vast white sand dunes, seasonal lagoons, and a mosaic of coastal and freshwater ecosystems. The river sits at approximately 2°39'S, 42°47'W, placing it within a low-elevation coastal zone where freshwater and estuarine environments intermingle. The Rio Sucuriju is part of the broader Preguiças river basin, a relatively small coastal drainage that nonetheless supports a surprisingly rich and diverse fish community, including both obligate freshwater species and estuarine organisms that move between the river and coastal waters.