Lund boat seat

[stomper]

I am going to replace one of the wood seats on my Lund ssv simply because I am building a storage box to replace it. I purchased a sheet of 5/8” MDO for the project as I want it to match up as close as possible to the stock seats as I can get it. Through all my research I have found out that this is the plywood they use but I couldn’t find anywhere on what they use to seal the wood. Does anyone have any knowledge as to what they use.