Well, I know that but this was still a surprise.
After I got my Puffin fiberglass dinghy at the beginning of the summer before last, I printed up a label on plain paper with my contact information. I set this into some wet epoxy and then applied more epoxy over it, wetting out the paper as much as possible, with a good thick coat over the top. I thought this would be a pretty permanent marking unless someone took a grinder to it. Wrong.
I noticed yesterday while cleaning the dinghy that the lettering was illegible. I touched the label and the top surface scraped off like a wet label from a food jar. There is still paper stuck to the hull but the rest is gone. This was up under the gunwale so a pretty dry location. I can't remember what I used but it was something like System Three or Silver Tip. The paper wasn't fully saturated but there was a thicker a layer over the top as I would expect to use in the finish of an epoxy composite wood construction.
Even when there is no standing water, moisture seems to migrate through Epoxy to a much greater extent than I would have expected.