If you do it every time you take the boat out, Babes Boat Bright is the best I've found so far. It doesn't do that well on the water spots though.

I have been trying a lot of different products trying to find something that shines as well but also removes the water spots. All the products I've tried are either thicker and more like a wax that require a second pass with a dry towel to bring out the shine, or just a quick detailer that doesn't do as well as BBB.