Thanks for the information, Super! I’m familiar with the techniques for making styrofoam terrain but I had never thought of buying it ready made. I’ll definitely have to look in to that!
The water sheets are another thing I’ve had difficulty finding. It’s less messy than the various liquid compounds or art supply materials like gloss medium or Mod Podge. On the other hand, the clear or blue tinted plastic sheets are sometimes shockingly expensive if you can find them through hobby shops and online retailers. Some, like Plastruct, seem to only be available in relatively small (say 3x5 inch) sheets for those shocking prices!