has more plys than A/C grade exterior plywood. That is a big factor in terms of strength, warping, etc. One thing that I have found is a good substitute for marine plywood for interior bulkheads that will be painted is MDO (medium density overlay). MDO is a fully waterproof plywood with a laminated surface on one or both sides for painting. It has more plys than normal exterior ply and very few small voids. It glues very well. The only down side I have found is that it is a lot heavier them Okume ply and even a bit heavier than Meranti.