Which river can you hike in Utah?

Context: Hiking The Narrows is arguably the quintessential Zion experience. The Narrows can be hiked either as a top-down through-hike from Chamberlain Ranch to the Temple of Sinawava, or as an up-and-back bottom-up hike from the Temple of Sinawava. Hiking is done largely in the river as, for a third of the route, the river runs canyon wall to canyon wall. Water levels change from season to season; most hikers will wade at least waist-deep and many will swim a few short sections. 

The Narrows is the narrowest section of Zion Canyon in Zion National Park, Utah, United States.

Answer: The Narrows at Zion National Park