The principles about direction of light in a painting and the corresponding shadows that are cast also apply to waves. The three photos here all show a wave that's approaching directly onto the shore, but in each the light conditions are different.
In the top photo, the light is shining at a low angle from the right. Notice how strong shadows are cast by parts of the wave.
The second photo was taken on an overcast or cloudy day, when the sunlight was diffused by the clouds. Notice how there aren't strong shadows, and how there isn't any reflected blue on the sea.
The third photo was taken on a sunny day with the light shining from behind the photographer, onto the front of the waves. Notice how little shadow is visible with such a front lighting situation.
