This one here on the left was done by applying Schmincke masking fluid to draw the ripples. I like that particular masking fluid because it comes in a little pipette dispenser and it's quite good for drawing fairly fine lines. I use the blue-tinted masking fluid rather than the transparent one, as I need to see what areas I've masked.
Then, once the masking fluid is completely dry, it's just a matter of applying a wash of colour (Schmincke's Helio Turquoise - PB16) with a big brush.
Neither is close to the original photograph, but this is a start at least!
I'm wondering if I should do a very very light wash before applying the masking fluid - a pale yellow and maybe some very pale red in some areas? To give the ripples more life?