Marine Grade Plywood is an structural plywood for exterior uses. The plywood are sanded on both sides, which commonly made from hardwodo or pine. Different species of hardwood may be used for marine plywood, usually in the Marine (boating) industry.

Plywood With No Voids
Marine grade plywood is constructed in exactly the same manner as other exterior grade panels except that the core are of a higher grade where any defects are repaired, leaving no voids or voids no greater than 1/8”. The same structural exterior glue is used and the face and back veneers are usually of higher grades.
Best Plywood For Wet Conditions
Manufactured from durable face and core veneers, with few defects so it performs longer in both humid and wet conditions. This veneer construction enables it be used in environments where the plywood is exposed to moisture for long periods.
Phenolic Glue Make The Plywood Waterproof
The marine grade plywood must use phenolic glue to make sure that the plywood is water boiling proof (WBP plywood). The reach a higher grade of water resistance, best quality phenolic resin should be used in the process of plywood manufacture. The lowest grade glue used should be melamine formaldehyde glue.
The phenolic glue features a dark glueline between the layers of veneers.