It's pretty safe to assume that no one's going to raft or kayak over Angel Falls, a waterfall that drops 2,648 feet (807 meters) off the side of Venezuela's Auyantepui Mountain [source: Angel-falls.com]. But there are plenty of other whitewater rapids out there that are navigable -- that is, if you're a skilled kayaker or rafter seeking a risky and exhilarating ride.
Most often, a river's "danger" is graded on the International Scale of River Difficulty from I to VI, with I being a stagnant lake and VI being the absolute limit of what you can conceivably run. On these rivers you'll find a mixture of fun and danger -- fun and danger that an estimated 35.6 million Americans take advantage of each year [source: AmericanWhitewater.org]. And a search through the American Whitewater accident database shows that, due to the much higher number of people rafting the easier waterways, the baddest rivers with the biggest drops aren't necessarily the ones that kill or injure the most people.
Rivers seem benign enough, but the ugly fact is that white-water rapids do kill. Nevertheless, intrepid boaters, floaters and/or oak-barrelers continue to throw themselves at them in reasonable numbers.
So which are the wildest rides?