Just FYI, this is a single shot with the top cropped off
This surprizes me, for the water line's curvature is pretty much to an 18mm lens - although if you have cropped off much from the top, then this part must have been quote low. You could correct this by a stitcher (stitching a single frame can mean correction of curvature - or the opposite, introducing of curvature).
Anyway, I would separate the sky and give it its own lightness and contrast (i.e. lighter than the base).