The Río Aguapey is a tributary of the Río Uruguay in the province of Corrientes, Argentina, flowing approximately 310 kilometers through a broad alluvial plain before emptying into the Río Uruguay near the town of Alvear. The river originates near San Carlos in the northeastern corner of the province, close to the border with Misiones, and follows a sinuous, meandering course southward. Its drainage basin covers roughly 8,106 km², and the river carries a mean discharge of around 83.6 m³/s. The channel traverses terrain with very little gradient, which gives the river its characteristically slow, winding nature.

The floodplain along the Aguapey is wide and dynamic. During the rainy season, roughly December through May, the wetlands on either bank can extend up to 5 kilometers on each side, creating an expansive system of bañados. This seasonal flooding directly affects water levels and paddling conditions; a gauge reading at the Ruta 40 bridge showed a relatively low level of 0.9 meters, which caused slow progress and occasional bottom contact.

Paddlers have organized multi-day traversals of the river in segments defined by road crossings. Put-in and take-out points include the bridges at Ruta Nacional 120, Ruta Provincial 37, and Ruta Nacional 14, among others. One segment between Ruta 37 and Ruta 40 covers approximately 93 kilometers of flatwater. Groups have camped on sandy beaches along the banks during these multi-day trips. A three-day paddle ending at the Ruta Nacional 14 bridge used sandbars as campsites.

The river supports a notable variety of wildlife. Fish species include dorado, surubí, sábalo, palometa, bagre, and tararira. Reptiles present include yacarés, freshwater turtles, and snakes such as the ñacaniná and curiyú. Fishing regulations have been introduced on at least portions of the river to protect fish populations, so paddlers should verify current rules before planning a trip that includes fishing.

The overall character of the Aguapey is flatwater paddling through remote wetland and gallery forest landscapes. Groups have traveled the river in kayaks and piraguas, typically in parties of multiple boats. The remoteness of the corridor means self-sufficiency is important, as facilities along the route are minimal.