Two parents take their son on a vacation and go to a nude beach. The father goes for a walk on the beach and the son goes and plays in the water. The son comes running up to his mom and says "Mommy, I saw ladies with boobies a lot bigger than yours!"
The mom says, "The bigger they are, the dumber they are."

So he goes back to play. Minutes later he runs back and says, "Mommy, I saw men with dingers a lot bigger than Daddy's!"

The mom says, "The bigger they are, the dumber they are."

So he goes back to play. Several minutes later he comes running back and says, "Mommy, I just saw Daddy talking to the dumbest lady I ever saw and the more and more he talked, the dumber and dumber he got!"