"Victoria Falls is over a mile (1.6 kilometers) wide and was in spitting distance from our put-in for a six-day rafting trip down the lower Zambezi, in Zimbabwe and Zambia. Once we got on that superhighway of churning water, our awe for the river intensified. Along the peaceful parts, we were followed by hippos and watched ten-foot-long (three-meter-long) crocs slip into the water. It wasn't until our raft flipped over that we truly experienced the wicked, foaming Class V rapids, a place where chaos reigns supreme."

Vivian and Temple Harris, White-water chasers
Six years ago the Toronto couple hatched a plan to raft the planet's 20 greatest white-water rivers. Temple, 57, president of a construction company, and Vivian, 54, a high school French teacher, began their pursuit by weaving through Alaska and the Yukon Territory on the Alsek and Tatshenshini. The Zambezi was their fourth river. This summer, they'll hit their ninth, Peru's Cotahuasi. In the winter, they work on another checklist: skiing the world's top 25 resorts.