Yosemite Valley, with the Merced River, sunlit meadows, mixed conifers and hardwoods, and looming granite cliffs, is one of the most incredible sights in all of North America. The Merced River tumbles over the Nevada and Vernal Falls before serenely flowing through the Valley. Though peaceful here the Merced becomes a class IV white water downstream as it tumbles out of the National Park and down the canyon to the California central valley.  Raft floating within the Valley, with stops at the beaches along the way, can usually be enjoyed from May to July  between Stoneman Bridge and the Sentinel Bridge.