Sketch rocks. They don't need to be too precise. Note most of the detail is in the lower half of the sketch.
Draw over the lines with a fine permenant marker. (test on the side of the paper to see that it doesn't
bleed when dampened with watercolour. Don't draw too precisely and don't worry if you have several
lines in one place this will look more natural.
Choose colour. I have chosen quite bright colours. madder Lake, Cobalt, raw sienna. But if you want a colder
atmosphere you could choose, burnt sienna, prussian Blue, raw sienna.
Paint over the lines allowing the paint to flow. Avoid painting inside the shapes. Leave some lighter areas.
Add more darks especially at the bottom of the rocks.
Paint the sand with raw sienna and allow to dry before painting another layer of blue. As the colour are transparent
the yellow will be visible through the blue layer.
Paint in the sky and sea with the same blue
Spray some darker yellow with a toothbrush on the sand and rocks
You can add more pen lines when the painting is dry.