Would be the keel, you're thinking of? Yeah, if you can, use regular wood, and seal it. If all you have is the MDF, then seal it also, with a good acrylic, or epoxy.
I will vote # 1, because he has spirit, and is adventurous!
And I am sure he has a life vest.
Now just think, if you had all the money you have spent on this boat, you could take your Girlfriend, to a nice little Pub, and have a steak and kidney pie, and a pint each, while enjoying a nice quiet conversation, unless there is a soccer game on the telly.
Or you could buy more beer, and cook her parents the rest of the fox.
But I do believe it will float. ........ for awhile at least.
Seal it well, sailor, seal it well! And beware of the Great Whites that frequent the channel!
Wayne