Seascapes to me are not just pictures of the waves. They include anything on the coast; details or sweeping vistas are all in the mix for me.
Working in monochrome makes it possible to emphasise those elements I want to bring forward without getting too hung up on representing their colour "accurately".
I will shamelessly boost shadows and highlights, adjust contrast and make changes to the relative luminance of the different colours in the original. Just as I did in the darkroom back in the day!