Painting and Sealing
With most methods, use either Hydrocal or hardboard under water areas. Then apply a basic sealer so that the you won't get leaks. Even though E-Z water and EnviroTex seem very thick when mixed, they will flow like water through any small hole in your base. Under E-Z Water seal the area with Flex Paste. Flex Paste works well under EnviroTex, too. And it gives you a nice white base to start with.
Next paint darker colors (black or dark gray) near the center and lighter ones (tan or gray) near the shores. Add rocks and turf—or even sunken objects like boats, barrels or branches, then seal the whole area with clear acrylic sealer (spray) or concentrated matte medium. This acrylic spray is important to preclude as many air bubbles as possible, especially if you use turf. Once the sealer dries, you're ready to pour EnviroTex or E-Z Water.
If the water is to be opaque, no lakebed/streambed features like paint or turf or underwater boulders are needed, but stumps or rocks that protrude from the water are. If the water would look better with color in it, stir in a very small amount and mix it in prior to painting/pouring, following the instructions that came with your water modeling material.
Color Mixing Suggestions
Our blue mix for streams and lakes is usually seven drops of EnviroTex transparent blue dye to about one teaspoon of Pollyterrain Gloss. Our color formula for oceans: Use Badger Opaque Airbrush Acrylics as follows: four drops Prussian blue (#7-30), one drop Chrome Oxide Green (#7-40), one drop (Amber #7-22). Use one drop of this mix per ounce of mixed EnviroTex. First mix that drop into the first part of the two part resin. This way with one part of the resin colored you can see when the two parts are well homogenized.
Tip: Be sure to put some newspaper on the floor to catch drips—even if you feel you've perfectly sealed the area. You'll be surprised at just how unlikely an achievement this thing called "perfection" is. Only EnviroTex, casting resin, real water, and E-Z water require meticulous sealing prior to pouring. Polyterrain Gel and Gloss and the other methods only require paint and other objects on the bottom for good effects.