Rule: horizons should be off center to create more interest and pleasing image.

By putting the horizon centrally here there is an echoing of land and sky giving tension to the image.

Both the treachery of the ocean and cliffs and the power of the sky have equal significance in the image.

We know that the rocks are "heavy" and by centering the horizon it gives the impression that the sky is also "heavy".

The eye is drawn to the center where the sky and land collide.