The back of an old frame provided some nice 1/8 inch board. It was surprisingly sturdy.
Liquitex Flexible Modeling Paste - Gel Medium smeared liberally.
I used the flat side of the blade against the putty and pull it straight off to give it a crinkly wavy texture. Process repeats many times until both squares are well-textured.
A hosing of blue spray paint followed by a thin black wash to create some extra "shadowy depths."
A couple drybrushings - pale blue, then white.
And a heavy gloss coat - job's done!
They look purty with the little boats. I'm rather happy with how these turned out. Now I need to make a couple for those land games!