They were all trapped on an island

There was a blonde, a redhead, and a brunette.

They were all trapped on an island and the nearest shore was 50 miles away.

The redhead swam trying to make it to the other shore she swam 15 miles, drowned, and died.

The brunette swam 24 miles, drowned, and died.

The blonde swam 25 miles, got tired, and swam back.