I seriously doubt someone other than a well-trained endurance athlete would tackle a nine mile ocean swim and have a remote chance of finishing.
Of course strange things can be accomplished when your life depends on it.
Elementary backstroke. What would really worry me would be sharks.
I think in this case, if you know you will die if you give up, you will keep trying. This man was also a professional athlete. One doesn't have much choice when faced with the inevitable.
Louie Zamperini of Unbroken fame, said, "Never give up, no matter what." If someone has it in them and is positive and wants to live, they can do more than you think.