Azul River: Class III/IV If the water levels are high enough, one of our first days is typically on the Azul River, a tributary to the Futaleufu. This is, by far, the most scenic river in the world. It winds for a 3 or 4 hours of paddling through a great series of class II and III rapids leading to a single class IV run. The highlight of this river is it's canyon section that winds around to an amazing view of the mountains!