Marine grade plywood if i am not mistaken should be Crezon. It should have a thin brown paper coating if it is raw.
It also comes pre-painted (although i am not a fan).
If you apply your vinyl to raw wood. It will fail prematurely.
Here we have 25 sheets of 1/2" Crezon with one coat of oil based primer and one coat of oil based paint. (lightly sanded and cleaned between coats)
Ready to accept full prints