Oh dear, what have I started. I've been laughing at myself all day, and now you're taking me seriously. Perhaps you should buy yourself that sense of humour. Or knitting needles.
Thanks for your advice. I'll be waiting for more beans of wisdom from both of you, that's for sure.
***Dog, I know this thread is a month old, but in case the OP hasn't found a solution I feel compelled to post***
You've got the answer right there! Stick a bean in it and the water will cause it to swell up and fill the hole. ;-)
Now for the more serious advice. I once had a wooden boat with a crack in the hull. Worse situation than a 3/8 hole if I do say so myself, though not nearly as funny. What I did was apply underwater epoxy to the crack. Now I had heard advice to get marine-tex and what I found was that like 5200 and a LOT of other products "cure underwater" does not translate to "apply and stick to" underwater.
What worked was an epoxy putty in a stick form. I think it actually might have been marine tex brand, but it was a stick form. It may be this same product under west marine's name.
West Marine: Epoxy Stick Product Display
Looked a lot like this:
Marine Epoxy Stick
Since I had an ablative (soft) antifouling paint, I had to scrape it off around the crack with a metal brush until I was down to bare wood. I did this with scuba gear. Then, I applied the bubble gum-like stuff, to the hull. If you press it on and smoosh it a little but don't mess with it too much it will stick. Believe it or not it stayed in place and the boat was bone dry for 4 years. I even took the boat on a 4 month cruise with the bubble gum repair on the 4ft crack and it never came off, even in a 1/2 decent storm. (Yes, that WAS stupid, but despite that the product worked)
This stuff is now my favorite repair-it-all product. Even better than duct tape. I've used it on a radiator fitting (lasted 5 years) on my car as well and can attest to it's temp tolerance.
Now I really like the suggestion of the butyl tape and bolt (with washer) idea. I've got no direct experience with butyl tape but from what I hear it is probably a good product for the purpose. Add a good sized glob of the epoxy putty over the top for insurance. Don't worry about removing it. Next time you're out of the water it'll chip off without much hassle.
Also, now is a GREAT time to install an automatic bilge pump if you haven't already. If you have, now's a perfect time to install the 2nd one and run the wires directly to your other battery. After 6 years of leaky wooden boat ownership I can't recommend RULE bilge pumps enough. Never had one fail despite the abuse I heaped on them and I had plenty of others fail.
Hopefully all is already fixed, and if not, good luck!