Before starting to paint water reflections, the whole of the river should be painted in a tone considerably darker than the sky. This will help them to judge the correct tonal relations of various reflections.
Calm diagnosis is necessary when making a realistic painting of water which has become frantic and disturbed by a powerful wind.
With oil painting, the problem can be solved in the initial stage by ignoring the restless movement of water and painting the reflections as they would appear if seen on a calm day. Then, with a brush fully charged with oil colour, paint the movement of the water, leaving certain passages untouched.