Two parents take their son on vacation and go to a nude beach.
The father goes for a walk on the beach and the son goes to play in the
water.

Shortly thereafter, the boy runs to his mother and says,
 "Mommy, I saw some ladies with boobies a lot bigger than yours!"

 The mother cleverly replies, "The bigger they are, the dumber they are!"
With that, the little boy runs back into the water and continues to play.

Several minutes later, though, the little boy runs back to his
 mother and says, "Mommy, I saw some men with dongs a lot bigger than
 Daddy's!"

 "The bigger they are, the dumber they are!" she replies.

 With that, the little boy runs back into the water and
 continues to play.

Several minutes later, though, the little boy runs back to his
 mother and says, "Mommy, I just saw Daddy talking to the dumbest lady I
ever saw and the more he talked, the dumber he got!"