A different idea
You didn't say how high it was riding, or what kind of boat it may be. I am assuming it is an older boat. It is very possible that some previous owner raised the water line on the boat. Many do this, as some cruisers have a tendancy to somewhat overload the boat. My last boat I raised the waterline 4 inches as I was one of those who sometimes overload. Keep in mind that the waterline, is just painted on, and is subject to the whims of whoever is holding the brush.