The negative space top of frame isn't working for me, negative space has to fulfil a active role in the sense that it has to further enhance the main focal aspect of frame, it just misses here....however, you have a superb mono square if that's your thing? Personally I think it would work as a lot better.
I take your point, and - in fact - have two versions, though this one has always kept my eye longer. For me, the presence of the "empty" upper part
serves to continually draw the attention away from the rocks, which you simultaneously want to get back to as the main part of the image. The slow oscillation from top to bottom to top again mimics the gentle rhythm of the quiet surf, which was really the point of the capture (a long exposure at dusk, with the boundary between "water" and sand essentially invisible.