The Río Chamiza originates at Lago Chapo, a deep glacial lake situated at the foot of Volcán Calbuco, and flows approximately 35 kilometers before emptying into the Seno de Reloncaví. The river is also known locally as Río Coihuín. Its source, Lago Chapo, is one of the deepest lakes in Chile at over 460 meters, and the river serves as the primary drinking water supply for the city of Puerto Montt.

In its lower reaches, the Río Chamiza transitions into an estuarine system that forms the Humedal Marino de Coihuín-Chamiza, a wetland of approximately 1,765 hectares influenced by tidal action. At low tide, intertidal flats can extend up to one kilometer across. This internationally significant wetland supports populations of migratory and resident shorebirds, including the Hudsonian godwit, whimbrel, and American oystercatcher.

The lower river and estuary are accessible from near Puerto Montt, making it a relatively convenient destination. Guided kayak descents are available through local operators, with at least one outfitter — reachable via the handle @leufuchamiza — offering organized trips on the river. The paddling character in the lower section is calm and accessible, suited to a range of experience levels. The tidal influence on the estuary means that water levels and current direction in the lower reaches will vary with the tides, a factor worth accounting for when planning timing.

The river corridor and surrounding wetland offer wildlife observation opportunities, particularly for shorebirds. The broader area around Lago Chapo also supports native forest and fauna including the pudú. Fishing for rainbow trout and Chinook salmon is noted as an activity on the river, which may be relevant to paddlers in terms of sharing the water with anglers.