Gel Coat only half way

I am taking a 94 sunfish Daysailer down to gel coat and refinishing the hull. Found it interesting that gel coat was applied to the bottom but not the sides of the hull. In stripping the barnacles and bottom paint off I found good gel coat across the hull up to the waterline. Very definite line from bottom to side then only paint on primer and fiberglass. Deck is good gel coat.