The most important thing to know is that it isn't some magical wood that doesn't rot. In most cases it actually isnt a very durable wood when it comes to rot. It is more susceptible to rot then domestic woods like southern yellow pine. Second most important thing to know is it is NOT treated with anything to keep it from rotting. So what makes it marine plywood? It's laminations. They are numerous, virtually void free, it's generally lighter in weight. Some cases, alot lighter. It's strength. It has a high shear strength. These panels are solid panels. The glue is a waterproof glue. You can boil a piece of marine plywood and then freeze it and it doesn't delaminate. Nice little fact to know. I've thrown pine plywood scraps out in the scrap pile alongside marine plywood. The marine plywood won't last near as long UNLESS you properly coat it with the proper product and it will outlast you. If you aren't going to spend the money for epoxy don't waste the money on marine plywood. You'll be disappointed with the end results.