Marine plywood is considered one of the toughest and most durable varieties of plywood on the market. It is used for building kayaks, boats, and docks. The plywood was designed to have a high resistance to moisture. The advantages of marine plywood are that it is strong, durable, and resists warping. The disadvantage is its cost. Prices range from $70 to $100 for a 4 x 8 sheet.
Determine what you want to use the marine plywood for. Then decide how much you will need in order to buy the correct amount and to be able to figure out how much money you will need.
Choose the thickness of the marine plywood. There are several kinds, and they will differ in thickness. For instance, Meranti is 1/4" thick, while Okoume is about 1/2" thick. They differ in weight as well. Okoume can weigh at most 16 pounds, while Meranti weighs at most 24 pounds. Depending on what you are making with the marine plywood will help you determine which type you will use. If you are making a deck, you will want the thickest and heaviest marine wood.
Check the marine plywood for knots. In marine plywood, knots are evidence of low-grade wood. Knots are circles in the wood that can eventually fall out and cause a hole.
Select a color for your wood. Colors will come by placing veneers, which are thin sheets of colors that are laminated onto the wood. Check to see if the compression of the lamination is perfectly lined up and compressed to the wood tightly. Be sure to check the color variation of the sheets. If the veneers weren't put on correctly, it will appear discolored. This will happen when the company didn't cut the veneers from the same sheet.
Look for evidence of voids. A void will be where moisture managed to get trapped in the wood inside bubbles or air pockets within the plywood.
Construct your subject using marine plywood. Once you have bought the marine plywood, then you should be able to build a strong deck or boat and expect the wood to resist warping. Provide a high gloss for extra protection to the marine wood, and to make it easy to clean the wood to keep it shiny. This is especially important for a kayak or boat.