Remember Diana Nyad, the...

...61-year-old marathon swimmer who set out for Key West from Cuba? She didn't make it, but it's a great story (my emphasis):

At 1:30 p.m. Monday, with the ocean swells now buffeting her, Ms. Nyad was struck by an asthma attack, her first ever, and struggled to breathe. But she kept swimming.

Nearly twelve hours later, halfway between Cuba and her destination of Key West, Fla., Ms. Nyad was treading water when she began vomiting. She then reluctantly allowed herself to be pulled aboard a support boat named the Bellisimo, where she was quickly wrapped in blankets. After swimming nearly 29 hours, Ms. Nyad abandoned her quest to complete the 60-hour, 103-mile journey, spread across three days, between Cuba and the United States.
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Ms. Nyad had trained and prepared nearly two years for this week’s swim. She swam 12 hours every other day; in between, she lifted weights.