River surfing on standing waves has been documented as far back as the mid 1970s in Munich, Germany and Jackson Hole, Wyoming. But I'm pretty sure that it was ( whitewater ) kayakers, just a few years ago, who thought of using stand up paddleboards ( SUP ) in whitewater.
This "new sport " is still in its infancy. But little by little the (R)evolution is happening, there are more people on SUPs in whitewater, and despite of all that mocking from "hardcore kayakers " whitewater surfing, SUPing and riverboarding are here to stay.
Even if you are not ready to "run a river", surfing standing waves looks like a lot of fun: