I need to replace some pieces in my boat and I was wondering if there are different thicknesses of marine plywood available. The pieces I have to replace are the tops of bench seats in my boat that are currently split and coming apart. They are covered in indoor/outdoor carpet currently and I don't have to cover them back up, although it wouild look better. Is there another material I could use in place of wood that is light-weight and durable? Can I use treated plywood in place of marine plywood? Decisions, decisions!