Denali Outdoor Center, Nenana River Canyon Run Excitement.

Paddle rafters brace for a plunge into Class IV whitewater. Paddlers work as a team and follow the commands called out by the boat captain. On this large volume river, you'll encounter a range of river features, including standing waves, big hydraulics, and swift current. Self-bailing rafts are designed specifically for these situations. (Credit Denali Outdoor Center)