Nyad has certainly chosen an arcane profession--she's about to swim from Cuba to Miami in July, and she does that sort of thing for a living. But, somehow, her autobiography makes the whole production of greasing up and stroking 60 strokes a minute for 16 or 18 hours at a time seem normal, so matter-of-fact is the account of her unusual avocation. When Nyad does a long-distance swim, she gets seasick, she gets frostbite, she gets badly paid, she gets viruses (from the polluted water when she swam around Manhattan Island), and she gets burnt. On one plunge into a northern lake the water was so cold that she was paralyzed and had to be pulled out of the water. The 98 degree heat of her rescuer's hands left an imprint on her shoulders that took days to heal. Still, Nyad perseveres. Never has a woman been so ""goal-oriented,"" and hers is to be the best-conditioned woman in the world. There are few who will dispute her. She plays squash in the off-season, trains for eight hours a day throughout the year, and still has time to party with Woody Allen (who asked to be introduced to her--he's an admirer), to write articles for many of the major magazines, and to write this, which is one of the most interesting sports biographies on record.