I faced some troubles with the rendering. I used Light Cache and an Irradiance map with medium settings. The Max Subdivs parameter was used to control the noise level on the final render.
Due to the pervasive Displacement maps, I had to increase the memory limit (Fig.07).
At the end, with my Core i7 and these settings, the render (2000 pixels width resolution only) took about 10 hours. At least I had no bad surprises!
This step was quite quick. As always, I rendered out Occlusion and Depth of Field passes. I also made some corrections with the Refraction pass, and used Photoshop's Burn/Dodge tool to increase the light and dark areas (Fig.08).
The final (and most annoying) step was to add some foam at the base of the ducks with a small, noisy brush (Fig.09).
As I said, there is no rational explanation to this picture; it's just a matter of interpretation. As Edgar Degas said, "Art is not what you see, but what you make others see.” What do you see?