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 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.
Better grades also tend to be lightweight strong and virtually free of defects.
That is it s not waterproof.
The cost of marine grade timbers compared to other types of materials can prove to be more economical with a properly engineered seawall or retaining wall lasting up to 25 years when adequately maintained.
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.
Marine grade plywood often simply called marine plywood is not what it s often claimed to be.
This also includes the treated material required to build docks and decks.
Pressure treated lumber has been synonymous with marine use for many years.
Marine deck is an optimal choice when only true wood will do.
Hope this helps i work in lumber at our local store.