When you run a river with a hydrology grad student (Brett Valle) whose main area of study is river holes and other features, you get a little bit different perspective on things. This photo was taken at the Flume, a short, undulating slide, on the Thunder Run. Brett pointed out the streamlined "supercritical" flow of the tongue of water, and how air was being entrained on the left side of the drop, and then pulled along the submerged ledge, finally erupting at the surface in pulses on the right side of the drop.

Below this point the water flows over another wave of granite and into a turbulent hole, joining another branch of current that comes in from the left. An eddy on the right can be used to setup for the second half of the rapid.