The Rio Ribeira, also known as the Rio Ribeira de Iguape, originates in Paraná state and flows approximately 470 kilometres before reaching the Atlantic Ocean near Iguape. Its upper course cuts through the Serra do Mar mountain range, producing turbulent whitewater that has made the river a recognized destination for rafting. Over the first 290 kilometres, the river drops roughly 900 metres in elevation through the mountains to the area near Itapeuna, after which it descends a further 90 metres over 90 kilometres to Registro, where it sits only about 5 metres above sea level. This dramatic gradient shift means paddlers encounter very different conditions depending on where along the river they put in — steep, fast-moving water in the upper reaches versus a much flatter, slower character in the lower sections.

Several named waterfalls punctuate the river corridor, including Cachoeira Das Andorinhas, Cachoeira Das Tres Quedas, Cachoeira Do Funil, Cachoeira Escondida, Cachoeira Nossa Senhora Do Carmo, and Cachoeira Queda Do Meu Deus. These features represent both points of interest and potential hazards requiring careful scouting or portaging.

The river passes through a relatively sparsely populated region with intact stretches of Atlantic Forest, and it supports several endemic fish species. No dams have been constructed on the river, which preserves its natural flow regime throughout its length.

Paddlers should be aware of a significant water quality concern: the river has been contaminated with heavy metals from mining activity to a degree that health authorities consider it unsafe to consume molluscs harvested from the river or its estuary. While this warning specifically addresses shellfish consumption, it reflects broader contamination in the watershed that paddlers should factor into their planning, particularly regarding any incidental water contact.