When painting water in a still state ie a rockpool, the easiest way to tackle it is to observe the dry light tones that sit on the surface and as the stone or rock is submerged there is a much darker shade as it sits below the water, this may seem a little brave when painting and too much of a contrast but the magic comes when you concentrate on the water line, just by adding a few spots of white or very pale tones of the colours above, contrasted with a couple of pin thin dark lines which outline the path the water takes around the rocks where dry meets wet, all will be revealed, and as i have put various weed around the edge, i have really detailed the form of the weed and under the water i have used flow enhancer on the wet paint and with a fine bristled brush have pulled the weed in a vertical direction and softened the detail to give the illusion of it floating freely under water. Check out my Time Lapse photography to see various stages in this painting.