There are two fishermen in a boat, Steve and John, and the boat starts sinking.  They can just about see shore from their sinking vessal. 

Steve says, "Come on lets swim to shore"

John yells in panic, "No, I can't swim!"

Steve quickly resolves the situation by saying "You lie on my back and I'll swim." 

Five hours later they get to shore and Steve collapses from exhaustion.  "Oh God!" he gasps, "I'm fucked!"

"Sorry mate," replies John, "but that's the only way I could hang on!"