To qualify that, it was my belief that you experience the delamination issues when non-marine plywood is used in applications where it is exposed to moisture. If properly coated on all sides/surfaces (to include edges), it seems to me that "regular" plywood should suffice.
I happen to know that there is currently a boat that I used to own on Craigslist that I totally replaced the floors, stringers and rear bulkhead (between engine and floor) with the $50/sheet Maple plywood offered at home depot. I coated everything on every surface after making all of my cuts and then epoxying everything down/together. That was about 5 years ago and I happen to know that boat has sat outside, with no cover on it since I sold it (RIGHT) after replacing all afformentioned wood, seats, carpeting and upholstery! Pretty sad, as the boat is beat now! But, this is making me want to go check it out and see if the wood has held up after at least 5 seasons in rain/snow/etc. Would be interesting to know if the floors are still solid, or if they are trashed. Its been a while, but I remember thinning my epoxy further than normal!
Nik