One of the big differences between regular and marine plywood is in the standards that are used to construct it. With marine plywood, the wood has to have a minimum number of voids in between the layers. It is also made with a special adhesive that is made to withstand water. Regular plywood is typically a little less expensive than marine plywood, and it also is not as dense and as well sealed as marine plywood. Some people put a special adhesive on regular plywood and use it in marine applications, but it still does not work as well as marine plywood.