Fishing Fools

Every day of their vacation, KRK & Vindu rented a boat and fished. One day they caught thirty fish.
KRK said, "Vindu, mark this spot so that we can come back here tomorrow!"
The next day when they were driving to rent the boat, KRK asked, "Vindu, did you mark that spot?"
Vindu replied, "Yep. I painted a big 'X' on the bottom of the boat!" KRK growled.
"You old fool! What if we don’t get the same boat today?"