Some fibreglass boats are still filled with spray-foam, and it has the known effects of eventually causing rot to any wood that might be embedded in the fibregl

Some fibreglass boats are still filled with spray-foam, and it has the known effects of eventually causing rot to any wood that might be embedded in the fibreglass. Embedded plywood is much less common nowadays though. (The foam cores in modern fibreglass construction is PVC-based, moisture safe, and can not be sprayed.)