The Río Trancura originates at Laguna Quillelhue and flows into Lago Villarrica, draining the southeastern side of the Volcán Villarrica National Park and the northwestern flank of Volcán Lanín near the Argentine border. The river receives volume from several tributaries, including the Río Maichin and the Río Liucura, and is the central paddling resource for the town of Pucón in the Araucanía Region.

The river is typically divided into distinct sections. The Upper Trancura runs approximately 9 km above the Pucón Kayak Retreat base and is rated Class IV, featuring pour-overs, boofs, slots, and two Class V big-water rapids — Marimon and Last Laugh — that attract expert paddlers. Notable features include Salto de Mariman, which is commonly portaged and accessible via a trail, and Salto de Feo. The last rapid before the takeout is the largest runnable drop and should be scouted from river left. Below the Upper section lies a Middle Trancura stretch of roughly 2 km rated Class II to III, with beaches and large eddies suitable for skill-building. The Lower Trancura is rated Class III and is appropriate for beginners and families, with the Pescador rapid being the longest and most notable feature. The confluence with the Río Liucura adds volume and produces Class III waves. The normal takeout for the lower section is the suspension bridge at Pasarela Quelhue, approximately 10 km from Pucón; shuttle drivers can be arranged through raft companies in town. The put-in for the Río Liucura confluence run is located about 20 km from Pucón at a public boat launch.

A solid combat roll is required for the Upper Trancura. The most common accidents on the Lower section occur at the first rapid below the put-in, where a rock bar has a difficult-to-see sneak line. Unattended vehicles at the Pasarela Quelhue bridge have occasionally been subject to vandalism, so arranging a shuttle driver is advisable.

The Upper Trancura is closed to commercial rafting in spring, while the Lower is closed in winter. The minimum age for commercial Lower Trancura rafting is 8 years, and 14 for the Upper. Views of Volcán Villarrica are a prominent feature throughout the run. A Mapuche market near the Lower Trancura takeout is a notable landmark. The Mariman Extreme Kayak Race is held annually on the river when levels drop at the end of the main tourist season.