Fishing Irishmen

Two Irishmen are out fishing, and are having great luck. They're catching fish so fast that they're forced to go back early.

"This is great Patrick," said Mick, "we should mark the spot so we can come here again."

"Right you are , Mick" Pat said. He then dived over the side, and scraped a big X on the bottom of the boat.

They head back to shore, and just as they're about to dock, Pat looks at Mick and says, "But what if we don't get the same boat next time?"