Just leave a bunch of primer sealed, epoxy sealed, shellac sealed plugs in the ocean 3-4 times. See what happens. You gotta seal properly!
Why go thru all the work of building plugs, just to have them split after a few uses?
Do it once, do it right
Sooner or later you're going to realize just as I did that there's a difference between knowing the path and walking the path. - Morpheus