Alan, off the top of my head, you might put a light into the water and then try playing with the bump of the water. Possibly a parallel light or a spotlight. Point it towards the wall then. Other way would be, as in that tutorial, to put a light above the water, point it towards the wall of the sewer and then put a gel on the light. Clouds or Difference Clouds (and then blurred) in Photoshop would serve well as the gel. It might be a faster way. I'd have to try. Nicely modelled. Rhino, I suppose? :-) BTW, why the oil looks like it's floating? Kemal, apropos the internal caustics, I'm not certain what you mean. Take a look at When the Music's Over in my gallery. There's nothing between the lights and the caustic pattern except the glass of the lamp.

-- erlik