More about painting shadows and reflections
When looking at shadows and reflections one is usually more dominant than the other. On wet sand the reflection can dominate. On dry sand there is no reflection just shadow. In figure 6 below, see how the shadow is not very distinct, this is because it is on the wet sand, shadows on water are generally quite pale, if not unobservable (when they are observable my camera is not sensitive enough to record them), and so I often leave then out entirely in my paintings.
Now in some cases depending on the time of the day, and the viewerâ€™s position; a shadow will be in the same direction as the reflection and is not so obvious e.g. when you are looking towards the sun with a reflection towards you. They will still create separate shapes but really all that will be seen is the reflection if the object is on water. On wet sand you may see both shadow and reflection but I would still just indicate the reflection.
Continue to: Color of shadows and reflections