The Rio Arinos is a significant river in Mato Grosso, Brazil, flowing for approximately 680 kilometers before it empties into the Juruena River. This river offers a substantial and remote paddling journey, as indicated by an expedition that spent 52 days traveling 620 miles down a route that included the Rio Arinos. The experience is characterized by a wilderness setting, requiring a combination of paddling, wading, carrying, and drifting, suggesting a varied and potentially challenging adventure through jungle terrain. Online paddling resources catalog access points for the Rio Arinos, indicating it is a recognized destination for kayaking and paddle boarding. The river is also noted for its fishing, with species like the Vampire fish, Trahira, and Piavuçu being popular catches. The river's coordinates are approximately 10°24′49′′S, placing it in the heart of the Brazilian state of Mato Grosso. Due to the expedition's description and the river's considerable length, paddlers should anticipate a multi-day, self-sufficient trip with logistical challenges, rather than a casual day outing. The surrounding area is part of the world's largest rainforest, implying a dense, natural environment rich in wildlife and untouched scenery.