Catholic Fish Bait

A man is walking along the beach at Portrush when he happens upon two Protestants holding a rope which leads out to sea. On the other end of the rope is tied a Catholic, who's splashing and shouting and drowning and making a terrible fuss.
'Hold on a second, fellas, says the passerby, 'I'll give you a hand to save this poor drowning man.' So he grabs the rope from them and hauls the Catholic in.
As he's walking away, one Protestant turns to the other and says: 'Who the hell was that?'
'Haven't a clue, said the other, picking up the gasping Catholic and throwing him back into the waves, 'but he doesn't seem to know much about shark-fishing!