Here is the medium I would like to present for Water simulation.

http://www.goldenpaints.com/products/medsadds/gels/gels.php

Extra Heavy Gel
These gels have the same characteristics as the Heavy Gel above, but they can hold better peaks and are ideal for impasto techniques. Along with the High Solid Gels, they are the thickest of the Golden Gels. Available in Gloss, Matte, and Semi-Gloss.

Molding Paste
Dries to a hard and durable, yet flexible, semi-gloss opaque film. Its consistency is similar to that of Golden Gels, but is slightly more rigid because of its higher density. Golden's Molding Paste holds stiff peaks to create highly textured surfaces.

Self Leveling Clear Gel - Designed to produce an even film with excellent clarity. The gel has a unique resinous, stringy consistency resulting from the leveling property. This product dries to a flexible, high gloss film, which can increase the transparency and sheen, while imparting a leveling quality to other GOLDEN Acrylic products. Blends with GOLDEN Acrylic colors to produce glazes.

P.s they can be the fine glue to make your own ground work.

William