does this composition work for you? I tried cropping out sand completely but then the surf comes very near to the edge of the shot and does not look good.
To me, this composition is really close. I do think there needs be a lot of extra "negative" space around the surfers, but i think there is too much sky in the one you've posted. I played around with the crop a lot and can't decide which way to go. What I think looks the best is cropping out the surf and placing the surfers in the extreme bottom right of the frame, but that loses a sense of place. The other option i've found is taking off some sky and some stuff on the left to just tighten up the crop a little bit, but not too much.