There is quite a bit of difference between Marine ply not just the glue .
BS 1088
Although a British Standard, it is used by marine plywood manufacturers world wide. The plywood does not have to be of British Manufacture. It is an extensive document which details all characteristics of the plywood.
The BS 1088 standard is a marine plywood specification that applies to plywood made from untreated tropical hardwood veneers that have a stated level of resistance to fungus growth.
BS 1088 plywood must use a glue, which has been tested and shown to be highly resistant to weather, micro-organisms, cold and boiling water, steam and dry heat. There are standard BS tests for the glue.
The Face Veneers must have a solid surface without open defects. Face veneers must be free of knots except "sound pin" knots, (no more than six in any one square foot,) the average of pin knots cannot exceed 2 per square foot over the whole surface of the plywood sheet. The grain in the veneers should be reasonably regular. Edge joints are limited, and end joints are not permitted.
Core veneers requirements are similar to face veneers except that slits are allowed as long as they are small. Pin knots and edge joints are also allowed. As in face veneer, end joints are forbidden.
Manufacturing Defects are strictly controlled. Poor bonds, overlaps and pleats, and gaps in faces are not allowed. Gaps may be filled using veneer inserts glued with appropriate adhesive.
The Moisture content of the plywood must fall between 6% and 14% when it leaves the factory.
Boards will be equally sanded on both sides.
Finished size The length or width of a standard sized sheet can not be less than the stated size nor more than 6.3 mm (0.25") larger.
Squareness -- The lengths of the diagonals of a sheet shall not vary by more than 0.25% of the length of the diagonal.
Thickness tolerances:
4 mm +.02/-0.6 ; 6 mm +.04/-0.65 ; 9 mm +.06/-0.75 ; 12 mm +.09/-0.82 15 mm +.1/-0.9 ; 18 mm +.12/-0.98 ; 22 mm +.16/-1.08 ; 25 mm +1.8/-1.16
Face Veneer thickness -- For any three-ply construction, each veneer sheet will not be any thinner than 1/8 of the total thickness of veneers assembled dry. Multi-Ply Construction-- This applies to boards thicker than 4.8 mm (3/16")
Each face veneer shall be a minimum of 1.3 mm and not thicker than 3.8 mm. Each core veneer shall be no thicker than 4.8 mm