I tried building one that way and wasn't happy with the results (probably more me and less of the design), so I made my own and incorporated the PVC as well as wood.
Here's a pic of it (at bottom): http://www.blueappleherps.com/page13/page13.html
And downloadable pdf on instructions (easily adjusted for whatever size tub you're using): http://www.blueappleherps.com/page13/page14/page14.html