The guy walks up and down the beach in his bathing suit and nothing.
Nobody looks. He comes back to his friend and the friend says “try a speedo”.
So he walks up and down the beach in his speedo.
Nothing. The girls aren’t reacting.
So his buddy says “take this potato and shove it down your speedo”.
And the guy does. He walks up and down the beach, and everyone is reacting.
Hot girls, ugly girls, the surfers, a guy walking his dog, the lifeguards, everyone.
The guy gets back and his buddy says “you were supposed to stick it in the front”.