Yeah also there is no chance that the slope is completely fall-line, so he would fly off the edge. And the velocity required for this would be too precise to risk by haphazardly splashing some water onto the surface in an uncontrolled way. Plus water would just increase resistance.
But yeah that gave me a good laugh. Just the look of a body flying off a ramp over a hundred feet through the air into an inflatable pool on the side of a mountain is priceless. I felt I needed to clarify to save some ego. Though the fact that I even had to explain to myself how it was fake does no good for said ego.