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. Several minutes later he comes running 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 !"