Once there were three girls on a deserted island. There was a red head, a brunette, and a blonde. Acorrding to their calculations, they were only 20 miles away from mainland. The brunette said, "I can swim pretty far. I am going to try to get to the mainland". So she gets in the water. She swims 5 miles and gets tired and drowns.
The red head gets in the water and tries the same thing. 5 miles, 10 miles, 15 miles. She is almost there but she drowns.
Then the blonde gets in. 5 miles, 10 miles, 15 miles, 16 miles, 17 miles, 18 miles, 19 miles, almost there only one mile away and she gets really tired .... so she swims back to the island.