Two friends rented a boat and fished in a lake everyday. One day they caught 30 fishes. One said to his friend,

“Mark this spot so that we can come here tomorrow”.

The next day when they were driving to rent the boat, the same one said,

“Yeah, I put a big ‘X' on the bottom of the boat”. The first one said,

“You fool! What if we don't get the same boat today”.