That is it s not waterproof.
Marine grade lumber.
Formed from high quality 1 grade dense 2x6 southern yellow pine dense select structural or 1 prime marine deck is guaranteed to be both attractive and durable.
Marine deck is an optimal choice when only true wood will do.
The 3 4 inch marine grade is 7 ply we dont carry the 1 2 inch but i would think it would be 5 ply.
Better grades also tend to be lightweight strong and virtually free of defects.
Marine deck boards feature a water repellent treatment for added protection in marine environments.
Pressure treated lumber has been synonymous with marine use for many years.
This also includes the treated material required to build docks and decks.
It is a good quality hardwood plywood made with waterproof glue but since it s not treated with chemicals it is not rot resistant.
Marine grade plywood often simply called marine plywood is not what it s often claimed to be.
Hope this helps i work in lumber at our local store.