Marine plywood is a sturdier also a higher-quality material made of Western Larch or Douglas-fir that is not treated with chemicals. This type of wood's thin sheets of veneer (plies) is usually set up perpendicularly as part of a process called cross-lamination that helps strengthen the material. Marine plywood is superior-quality hardwood plywood that is specially treated using paint, preservatives, or varnish to resist water damage. Marine plywood is constructed out of the finest grade of naturally water-resistant tropical hardwood.