When 6th-century Greek philosopher Heraclitus observed that you can't step in the same river twice, it wasn't the Colorado River he had in mind. But the Colorado looms large in Robb Moss's poignant documentary about a group of friends who took a month-long river trip in 1978, and what became of them 20 years later. Moss, Danny Silver and her "summer boyfriend," Jim Tickenor, Barry Wasserman, and blissful couple Cathy Shaw and Jeff Golden joined several others, all professional summer river guides, on the trip. They rafted, ate, hiked, camped, climbed rocks and hung out, usually nude and always on a casual, "where the day takes you" schedule. Aspiring filmmaker Moss d...