Yes, wave power preserves environmental beauty, because wave power only harvests the energy that is already there. Wave power does not destroy waves. It does not change a landscape. Wave power only capitalizes on the natural forces that are already in motion. Wave power cuts down on oil power, so it preserves natural beauty.
Certainly wave power installations are not the most beautiful things, however we are currently polluting our environment very badly with fossil fuels, which certainly destroys environmental beauty. From that point of view, wave power is certainly a lesser evil and if it can generate a lot of power with a reasonable use of coastline, it could be said to preserve environmental beauty. It will not preserve it everywhere, but it will preserve it in many places.