I bought these pieces from the Broken Egg booth at Adepticon. They’re resin and 3D, but quite flat. It gives a lot more depth than the neoprene terrain Broken Egg also sells, but is highly playable.

It doesn’t really show in the photos, but I coated the water in gloss Mod Podge then blew on the surface with an airbrush. It gives it a slightly rippled texture that helps to sell it as water.