I got down to the bottom of things. The pool was built in the 1970's with a plastic bullnose coping and integral liner track. Over the years, at some point, some of the plastic liner track broke and so when the liner was last replaced, a metal track was screwed to the wall below the original coping/track. Where the plastic track broke away, there is a 3/4" open space with sand, etc coming out (between the coping and the new metal liner track). The person I spoke with said to fill the area with white silicone caulk. Is there maybe a little more aesthetic solution than just caulking the space? Thanks again