Westwater Canyon is a seventeen-mile stretch of the Colorado River in eastern Utah, known for a one- or two-day whitewater trip through steep canyon walls and a dramatic inner gorge. In the Marble gorge, the river compresses into class III and IV rapids, with Skull considered the standout challenge, and the narrow vertical walls make rescues difficult. The canyon is also geologically distinctive: beneath Triassic and Jurassic formations, a major unconformity exposes black Vishnu Schist and pink Zoroaster Granite. Along with nearby Ruby Canyon, it is the only place on the Colorado River outside the Grand Canyon where Precambrian rocks are visible.