CHILE White-water raftingin thewinter? Hell, yeah. In northern Patagonia, the Rio Futaleufu snakes out of Argentina and into Chile for 100 miles before dumping into the Pacific.The “Fu” isCaribbeanclear, a soft emerald green. and along 50 miles of its nastiest twists and slides, Eric Hertz will take you bucking over the best class IV and v rapids in the Americas-quite possibly in the world.