I'm new to making water bases and have experimented with a few techniques that I have learned from. My first attempt at a water base used a technique featured in the Nov. 2004 FSM, which calls for using a crumpled piece of aluminum foil to form a surface of waves, painted blue, then coated with Mod Podge decopage glue/sealer (sort of a watered-down white glue) that dries clear and shiny. While not the best results I've seen, it worked okay and gave me something to build on. The photos of this technique from the FSM article looked pretty good and inspired me to give it a try. It was certainly fast and cheap, and there was no shrinkage to contend with! Here's a few shots of my results. The first photo is from an HO scale industrial model that that features a barge dock. The second and third photos are a 1/350 scale WWII era C2 stores ship.
The ship base was modeled to be a relatively calm sea state, with the ship having little to no headway. I saved that for the next technique -- acrylic gel medium -- after reading many articles, scouring this forum and others, and looking at the photos of many displays. I like the results of the acrylic gel medium, but it definitely took me more time and a bit more experimenting. I just finished a display base with it, but have not taken any photos yet. I am very pleased with the results, but again I learned a few lessons here and there, and will definitely apply those to the next project. The gel medium did not shrink on me at all, although I did notice that the wave peaks seemed to tighten, or crease more sharply, as they dried. Actually, I just had the idea that once I sculpt something in acrylic gel, I should take a heavy piece of aluminum foil and make an impression of it for a future project, then perhaps go back to the foil technique! Don't know how well it will work, but figure it's worth a try. I have not tried any of the clays, plaster, etc., but may progress to that at some point. I applied the gel medium by first painting a base with three different shades of blue. I gave it a coat of an azure blue, followed by two shades of progressively darker blues, applied with a dabbing sponge, with the lighter shades peeking out of the darker ones. I then applied the gel medium over the painted base, sculpting waves as I went along to represent a relatively calm sea state. After planting the ship on the base, I then proceeded to form the ships wake patterns about the hull, using a photo of the real ship underway for reference. I did not paint the surface of the gel as some do, but left it unpainted. I like the translucence of leaving it clear, although I thought of using a little blue food coloring mixed in. After it dried, I went back and dabbed the top with gel using a stiff brush to break up the reflectance a bit and put it more in scale with the 1/700 ship.
By far the best water base display I've seen is MFSOB's SS John Randolph -- just a superb job. He's on this forum, you may want to ask him for a pic, it's awesome. I hope I can get that good!