A boy from Duluth, Minnesota named Lars had heard stories of an amazing family tradition. It seem that his father, grandfather and great grandfather had all been able to walk on water on their 21st birthdays, to the boat club across the lake for their first legal drink.
So when Lars' 21st came around, he and his pal Sven took a boat out to the middle of the lake. Lars stepped out of the boat and nearly drowned. Sven managed to pull him to safety.
Furious and confused, Lars went to see his grandmother. "Grandma," he asked, "it's my 21st birthday, so why can't I walk across the lake like my father, his father, and his father before him?"
Granny looked into Lars' eyes and said, "Because your father, grandfather and great-grandfather were born in January. You were born in July."