blonde swimmer

There was a blonde, a brunette, a red-head and a bald¹ woman stuck on a desert island.
The brunette decided² to swim home, but got 1/3 of the way there and drowned, The red-had decided to try, but drowned 1/4 of the way there. The blonde decide that she had to risk it, so she swam 1/2 of the way there when she stopped and swam back.
"why did you come all the way back, when you were half way home?" screamed the bald woman. "well", said the blonde "I was going to carry on, but I got tired and thought I'd rest first".