Two Irish blokes are fishing. Paddy reels in his line and sees that he's snagged an old bottle. As he's taking it off the hook, a genie pops out and promises to grant him one wish.
"Turn the lake into beer," he says.
The genie goes "Poof!" and the lake turns into beer.
He says to his friend, Murphy, "So what do you think Murphy?"
Murphy says, "You fool! Now we've got to piss in the boat."