How many balls are there?

Fred and Luke were fishing on the side of the road. They made a sign saying:

THE END IS NEAR! TURN YOURSELF AROUND
NOW BEFORE IT'S TOO LATE!!

…and showed it to each passing car.

One driver that passed didn't appreciate the sign and shouted out his window, “Leave me alone you nuts!”

All of a sudden they heard a big splash.

Fred turned to Luke, “do you think we should just put up a sign that says: ‘Bridge Out Ahead' instead?”