The first thing I do after finishing the drawing is transfer it via light box onto the watercolor paper. Then I "ink" it with acrylic paint to make the line work as you can see on the left. In the right image you can see I started to lay in the shadows on the girl. This is all acrylic wash.
It's hard to tell, but on the left I strengthened the core shadows in the same areas. On the right I added the shadows to the fish and the ocean.
On the left here you can see a printout where I drew some test clouds in before painting them in on the right.
And here is a scan of the underpainting. This is as far as I take it with acrylic washes. Next post I'll bring it to final with concentrated watercolor.