[math-fun] Anyone who fell in would die

http://www.reddit.com/r/videos/comments/1dqcbf/how_to_cross_a_river_with_two... This much current could be converted to an asset. River fording is an ancient, universal problem. In all these intervening centuries, has no one thought of anchoring a(n unpowered) skiff with a tiller on a long rope running upstream? With ropes to both shores in case you find it not on your departure side. --rwg