Some rivers are fed exclusively by glaciers and require year round hypothermia protection like the NRS Endurance Pants. In AK, the whitewater is always cold enough to kill you. That's why NRS made the Endurance with waterproof breathable 2. 5 layer ripstop HypoTex fabric. If you get tossed off the raft into the heart stopping cold water, the single pull waist drawstring and adjustable ankle cuffs will seal out the barely liquid water from your most cold sensitive parts. Double fabric in the knees and a Cordura reinforced seat extend the life of the Endurance, while its loose fit enables easy layering.