Watch National Geographic- Iceland River Challenge for Free: How to Stream the Movie Online at 123Movies. . A remarkable film from the National Geographic's daring EXPLORER series, ICELAND RIVER CHALLENGE follows twelve modern-day pioneers on a treacherous expedition down a remote Icelandic river. Crash through waterfalls and glide through sparkling glacial tunnels on this breathtaking journey. Using kayaks, inflatable rafts, and ultralight aircraft, the adventurers journey through the beauty and isolation of this dangerous waterway. Come explore a river that has, until now, defied exploration; witness the heart-stopping power of nature in all its glory with ICELAND RIVER CHALLENGE.