Back to the OP, moisture meters are fantastic. If you don't have one or don't want to find one, do the test holes. If those are good, button it all up, but you don't want to be doing that every year.
The one good thing about water is it is relatively heavy. Weigh the boat after you have tested it. Take it to a truck scale as empty as possible, note your fuel level, and get a baseline weight. Make sure it is reasonably close to the dry weight that the manufacturer spec'd. After that, weigh it with the same load periodically and see if it gains weight. When the foam starts to saturate, it will be easy to see.
The one good thing about water is it is relatively heavy. Weigh the boat after you have tested it. Take it to a truck scale as empty as possible, note your fuel level, and get a baseline weight. Make sure it is reasonably close to the dry weight that the manufacturer spec'd. After that, weigh it with the same load periodically and see if it gains weight. When the foam starts to saturate, it will be easy to see.