Well, any exterior grade plywood (which is what he should use, of course) has waterproof glue. Marine plywood is more expensive than even cabinet grade plywood because it must have no core or edge voids, usually more plys than ordinary plywood, fully plugged knots on faces, etc. It's more of a structural distinction than a glue distinction - they may even use the same glue as ordinary exterior grade plywood.
The APA site has more information than most of us need/want.
http://www.apawood.org/Additional Info here, perhaps:
http://www.canply.orgRegards,
Tom