Just a thought, what about using cedar? I know it costs more, but it naturally resists rot and decay. There seems to be a big confusion with pressure treated and wolmanized wood. A quick google search does clear it up, however after working at a lumber yard for several years as a "kid" I wouldn't have trusted me back then if Some one said I need pressure treated wood or wolmanized wood. Especially a big box store especially if it's a matter of my tin boat developing holes over the years. Whether they were educated in the difference between the two or not (kid or adult). That's a chance I'm not willing to take. So would cedar be an alternative? If so I think it would be money well spent for some peace of mind. Just a thought.