I know this is kindof off topic but i didn't know where else to put this. I have a few large sea shells from a snorkeling trip in mexico. How do i get them to look like the ones you buy? They had some stuff growing on them so i soaked them in bleach and scrubed them but they are no where near as shiney and polished as the ones you buy from suvenier shops. Does anyone know how they clean them?