Gel medium can be used to model realistic water, but it can be expensive. I use Sobo, a craft and fabric glue made by Delta. It dries to a glossy finish and it behaves like rubber. Drying time is fast, and it can be easily painted. You can texture it to make waves before it completely dries; if you pour candle wax first, you can depict ordnance impacts. Always wear eye protection to guard against splashes.
Tip submitted by:Jasper Cole-KinkWest Stockbridge, Massachusetts