"Peter Dohm" wrote

Even if it was "marine plywood", which I think that I may have heard at some
point, I believe that the term "marine" only specifies that the glue between
the plies is not water soluble; so an acceptable grade of plywood may not be
as close as your nearest "Borg".

Marine plywood also has a higher quality standard for the inner plys, with a
higher standard of species allowed in the interior plys allowed, and no voids
allowed, although they are allowed to have plug repairs in the inner plys, as I
recall.

The glue in marine plywood does have to be waterproof, but more significantly,
remain strong while submerged in water for some specified period of time.

I don't believe that marine would have been specified for the glue content, most
likely. It is probably specified because of the higher guarantees of strength
and consistency.

Any plywood meant for construction that bears an "X" in the name has waterproof
glue, but it will have voids and repairs allowed, varying with the grade. CDX
is a common structural grade of plywood that has plugs on the C side, and filled
repairs on the D side, with the most knots and defects allowed in commonly
obtained grades.

Any plywood the bears a B or A grade will also have waterproof glue, unless it
bears an interior marking in addition.
--
Jim in NC