Posted by: Youtube user Sac Naksavath
Full description from National Geographic's website:
Dr. Zeb Hogan travels to one of the world's largest waterfalls in Laos, where each year millions of fish climb the falls to spawn. But little is known about their exact migratory route, and plans to dam the channel could place the lives of the fish, and the millions of people who depend on them for their livelihoods, at risk. Zeb and a team of world-class kayakers navigate the waterways with specially equipped kayaks, designed to take measurements of the rivers below them.