Paddy and Sean are out on the Irish Sea, in a rowboat fishing.
After a few hours of drinking and fishing, Sean falls asleep.
While Sean's sleeping, Paddy hooks something HUGE on his line, and after about 20 minutes, finally reels it in to the side of the boat. When he looks down, he sees that he has caught a mermaid. The mermaid looks at Paddy and says,
"Sir . . . If you find it in your heart to release me, I will grant you anything you wish."
Paddy says, "Tell me, fair mermaid, can you turn the Irish Sea into GUINNESS ?"
"Yes . . . if that's your wish.", she replies.
Paddy unhooks the mermaid and says,"Okay then, I wish the Irish Sea be turned into GUINNESS !"
The mermaid mumbles a few ancient words, does a tail slap, and says, "Your wish has been granted.", and swims away.
Paddy dips his mug over the side and fills it up. When he tastes it, sure enough, it is Guinness.
He starts shaking Sean, yelling, "SEAN ! WAKE up, WAKE up!"
When Sean wakes up, he asks Paddy, "WHAT the F*#K is wrong with you ?"
Paddy tells him about the mermaid, and Sean says, "You are fookin looney, man !"
"No. No . . . See for yourself", says Paddy, and hands Sean an empty mug.
Sean dips it over the side and takes a long drink. He realizes that it is, in fact, GUINNESS.
After a few seconds, he looks at Paddy and slaps him up side the head.
Paddy, a bit shaken, says, "What was THAT for?"
Sean says, "Ya daft bastid . . . NOW we're gonna have to piss in the boat !"
