Two friends rented a boat and went fishing in a lake. The first
day, they caught 30 fish. As they were preparing to go into shore,
one man said to the other, "Let's mark this spot so we can come
here again tomorrow."

The next day, when they were driving to rent the boat, the same
guy said, "Did you mark that spot?"

His friend replied, "Yeah, I put a big 'X' on the bottom of the
boat."

The first one said, "That was dumb! What if we don't get the
same boat today?"