Marine plywood to BS 1088 is manufactured using timbers classified as moderately durable or better (or exceptionally, gaboon) and with high quality veneers bonded using phenolformaldehyde adhesive (WBP). These plywoods are available from UK, Israel, France, Singapore, Malaysia and other sources. As a very high quality material, the downside is it can be expensive per sheet.

Initially marine plywood was developed for ship/boat building and can achieve a very high performance under severe exposure conditions, when properly sealed. It is also commonly used in construction applications where high performance is required or where the cost of replacement or consequences of failure warrant the additional cost.

In relation to the standard BS 1088, this has been superseded by a European standard since 2013. In regard to marine plywood the european standard is now EN 636-3, EN 314-2, Class 3.You are advised to check the suitability of both the bonding quality En 314-2 and also the biological durability En 636 prior to purchasing any product.

To clarify: The glue used in Marine Plywood is the same as used in exterior grade plywoods. Its the quality of the veneers (plies) and the durability of the species of timber used  in the veneers (plies) that make Marine Plywood better than ordinary exterior grade plywood.