Rivers provide the essentials of life: fresh food and water. They often provide natural highways and enable us to live in just about every environment on earth. But rivers can also flood, freeze or disappearaltogether!Human Planet joins Sam Niang, a Laotian fisherman, as he walks a high wire strung above the raging Mekong River rapids on an extraordinary commute to work.There's also a look at the remarkable partnership between Samburu tribesmen and wild elephants in their search for water in the dried-out river beds of northern Kenya.Also in the programme, a father takes his two children on a six-day trek down a frozen river as part of the most dangerous school run on Earth, and the ice dam busters of Ottowa provide a dynamite solution to a city centre hold-up.