In September, 2011, Diana Nyad, who Ariel Levy profiles in this week’s issue, attempted to swim from Cuba to Florida for the third time. Conditions were ideal: the weather was calm, the water was placid, and all was progressing as planned. As Levy writes, “Suddenly, at about 8 P.M., she felt a pain like nothing she’d ever experienced—like being ‘dipped in hot burning oil and your body is in flames.’ Nyad had been stung by a swarm of box jellyfish, the most venomous creature in the ocean.” Timothy Wheeler, Nyad’s nephew, was on the boat filming for his documentary, “The Other Shore: The Diana Nyad Story,” released late last year. Wheeler’s camera was rolling when Nyad was stung; here is an excerpt: