Here's a quick walkthrough of some thoughts on drawing water at the battlemaps/building scale. I was thinking about +Mike Schley's water style (like this map here: [link]
Around the edge of the water area, draw in smooth flowing lines. Draw them quickly with a sweeping motion - don't think too hard about it. This takes a little practice, but once you've got the hang of it, it comes quickly. Have the lines loosely follow the edge of the water, and avoid any sharp corners
At this point you can use it as-is - black and white line maps are easy and quick to use. But if you want colour, read on.
2. Base colour
Here I've added a grey blue as the base (on a new layer under the lines). Once the blue is in place, I added a white highlights, following the black lines for the edge of the ripples. I've added the white only to the edge away from the side of the pool. This way the ripples look like they're heading towards shore. Add brighter highlights right along the ripple edges.
3. Extra credit
In this step I've added the ripple texture from earlier this week as an overlay layer at 8% opacity. I've also added a new overlay layer and used a large fuzzy brush set to black and low opacity to darken the deeper parts of the pool. This will darken the blue, and bump up the saturation, but leave the white highlights almost untouched.
That's all there is to it! More tutorials on the Tutorials section of the blog: [link]
Have a good weekend!