Mmm... interesting questions! I would worry about using epoxy glue on a crystal and bezel - perhaps a rubber gasket might be an idea, if you can get one to fit
To be honest, I never use a watch in water - even one marked as waterproof or water-resistant. If I needed one for swimming, diving, etc., I'd buy a specific, sealed and waterproofed movement for the job. That was one of the attractions of the early plastic Swatch watches - great for those beach holidays.
It's actually possible to buy quite cheap watches which are water-resistant - but I admire your "madcap" idea. Have a go! :rock: