Artwork made for Blender Guru, to demonstrate the recently launched Rock Essentials pack;
Get yours here: http://www.blenderguru.com/product/rock-essentials/
All rocks found there came from the pack, so the bulk work of what could be a really long scene to create could be achieved in roughly two weeks, with most of the time being devoted to composition and the water setup.
All the water and mist/foam are coming from the render, no fancy post-production here. The water splashes, mist, foam and waves are all alpha masked planes and shapes, with splash/foam samples taken from pictures or hand-painted.
Strongly influenced by the tolkien universe/weta work (as everything else I do), turbulent waters won't stop barrel riders :)