One of the fundamental composition decisions in a sea painting is selecting the direction the waves approach the shore. Are the waves going to come in directly towards the shore, and thus the viewer of the painting, or at an angle? It's not a question of one choice being better than the other. Just that you need to be aware that you have got a choice.
Make a decision about this, then ensure that all the elements you paint (waves, open sea, rocks) are consistent in direction according to this, all the way into the distance.
