The one thing that seems to work best for me when I’m working with waves or a seashore is to have a decent foreground. Without that, things often fall flat, as in the following shot.
But if I can find something that’ll pull my eye through the scene, I usually like the result a lot better, as here.
Even something simple can work! Like just these rocks.
Without that all I ever get is lackluster shots, which honestly work better as abstract white and blue combinations.