Swim: Why We Love the Water. By Lynn Sherr. PublicAffairs; 224 pages; $25.99 and £16.99. Buy from Amazon.com, Amazon.co.uk

HAVING neither flippers nor fins, nor any form of gills, humans are not natural swimmers. Yet over the centuries they have happily thrown themselves into the English Channel and the straits of Gibraltar and Messina; they have swum round Manhattan, across the Sea of Galilee, and through the dark southern Atlantic from Robben Island to Cape Town. Every year, in early autumn, more than 27,000 people embark on a mass swim across Sun Moon Lake in central Taiwan, most of them using flotation devices. Nearly 52m Americans swim at least six times a year, making it the third most popular sport after walking and working out.

At 69 and with a duff knee, Lynn Sherr, a correspondent with ABC News, could have availed herself of one of the 10.4m private pools in the United States. Instead, she became determined to swim the Hellespont in western Turkey. Never mind that her route lay across more than six kilometres of choppy tidal water and Ms Sherr had not swum more than a kilometre in decades. There was something about the famous channel that separates Europe from Asia that caught her imagination. The ruins of Troy stand on one side, on the other memorials to the men who died in the Gallipoli campaign. Perhaps for Ms Sherr the call had to do with the Greek myth of Leander, who secretly swam the waterway for a night of romance with his great love, Hero, only for them both to drown. Or maybe her inspiration was Lord Byron, whose crossing of the same stretch in 1810 led him to write to a friend: “I plume myself on this achievement more than I could possibly do on any kind of glory, political, poetical or rhetorical.”

Ms Sherr weaves notes from her year of magical training for the Hellespont swimathon into a highly readable celebration of man's watery history and the lure of the blue—what Wallace Stevens called “the basic slate, the universal hue”—that has attracted swimmers from Neptune to Nemo. Thus the reader learns that President John Quincy Adams swam stark naked every day in the Potomac at 5am, and may have given his first interview under duress. It is said that Anne Royall, America's first female professional journalist, stole his clothes and sat on them on the riverbank until he had answered all her questions.

The author also recounts that Julius Caesar (at the time in his 50s) swam nearly 300 metres or six lengths of an Olympic pool with his sword and purple cloak clenched between his teeth, apparently holding his official papers dry above his head; that 2m people turned out in 1926 for the biggest ticker-tape parade Manhattan had seen after Gertrude Ederle, “a 19-year-old New Yorker with a slick crawl and a winning grin” became the first woman to swim the English Channel, setting a speed record for both men and women that would hold for 24 years; and that, contrary to urban legend, there is no known chemical that instantly turns pee in pools purple or any other colour. Unfortunately.

What makes this book far more than a Googled list of watery factoids is Ms Sherr's energetic focus on the newest swimming research and her articulate devotion to swimming as a way of life. She visits the Brain Science Lab at Indiana University, which studies the hard- swimming members of the US Masters: men and women who swim 3,500-5,000 metres three to five times a week, sometimes for decades on end. She talks to Olympians and to open-water champions like Lynne Cox to find out why they live to swim, why swimming is man's most sensuous sport (because skin is his largest sensory organ) and why it keeps your arteries elastic, your joints supple, is good for your heart as well as your brain, and offers more than a cursory help in the fight against ageing.

Although she had swum regularly for nearly 25 years, Ms Sherr realised she had to improve her efficiency in the water if she was to complete the Hellespont crossing. She spoke to coaches, such as George Block of San Antonio, Texas, who was recommended as an excellent explainer, and Jane Katz, a New York expert, who offered an array of small tips to make her more agile. She drove up the Hudson Valley to meet Terry Laughlin, a coach who is the talk of the internet. Preferring a holistic approach called “Total Immersion”, Mr Laughlin uses a video camera to analyse swimmers' problems, and urges them to stop using their arm muscles to push water molecules behind them and think of their arms instead as a tool to separate the water molecules in front. “Try to be gentle and light and gather moonbeams,” he told her.

Paul Valéry, a French poet, critic and essayist, summed it up best. Swimming was his love, the sea his lover. “In it, I am the man I want to be,” he said. For Ms Sherr, it was the official T-shirt offered at the end of the Hellespont crossing that spoke most eloquently: “Leander, Lord Byron…and ME!” Try prising that one off her back.