We’ve never seen anything like this before.”The other extraordinary thing about her is, of course, her ability to resist cold. Most people, when exposed to water colder than about 10C, lose body heat with extreme rapidity and go into hypothermic shock. Even relatively temperate ocean waters will do them in over a relatively short time. In Cox’s case, though, her core body temperature is actually capable of increasing over the course of a long swim. That’s not true in the harsher conditions of Alaska, or Siberia, or the south Atlantic, but even there her body has a remarkable ability to redirect its heat to the vital organs of her brain, chest and abdomen.

After her limbs have gone blue and splotchy – like a corpse’s, as she observed during her Bering Strait swim – her metabolism keeps going with remarkable strength, and with it her ability to keep pushing forward through the water.Cold is, in many ways, her most comfortable medium. Since her book came out in the US last year, she has been spending a lot of time on the corporate lecture circuit and staying in hotels with heated pools “They roast me alive!” she says, only half-jokingly. She doesn’t have especially fond memories of another politically momentous swim, from Egypt to Israel and from Israel to Jordan, right around the time of the signing of the Israel-Jordan peace accord of 1994. “The water temperature was about 80F and the air was about 90F,” she says with obvious distaste. Standing out here on the wind-blown shores of a distinctly tepid Pacific, it sounds pretty ideal to me.

Then again, if I ever visited Siberia, I’d never think to pack a pair of swimming trunks.As the book makes clear, Cox’s life has been little short of extraordinary. She broke the record for crossing the English Channel when she was just 15, reaching what was, at the time, her life’s ambition before she was even old enough to drive. She dodged predatory sharks in the Cook Strait between the North and South islands of New Zealand, faced more sharks as well as yellow-bellied sea snakes off the Cape of Good Hope, was bitten to pieces by mee fleas – a form of microscopic mosquito larva – in Lake Myvatn, Iceland, and used her bare arms to chop through pan ice in Glacier Bay, Alaska.Sometimes the obstacles were as unexpected as they were unpleasant. In 1990 on another symbolic swim, along the Spree between East and West Berlin, she had to dodge mines and razor wire, not all of which had been cleared out of the river after the Wall fell and the city was reunified. Even on the surface, she had to contend with dead rats and condoms.In Cairo in the early 1970s, a race down the Nile turned into the closest thing to disaster she has ever faced.

Having developed dysentery during her practice swims, she became dangerously dehydrated and eventually had to pull out – not before negotiating sewage-strewn water, more dead rats and the rib cage of a dead dog that she accidentally punched her hand through.The determination that Cox brings to her sport is not something that gets in the way of her relations with her fellow humans. On the contrary, her personality is every bit as buoyant as her body. Her impulse is not to aggrandise herself but to dig out what is extraordinary and fascinating in others, in much the same way that she has, during her toughest challenges, dug for the extraordinary within herself “Your body is so amazing,” she says with genuine wonder. “It wants to survive so bad.”The use of the second person is characteristically telling; Cox is not interested in promoting her own exceptional ability so much as the abilities of human beings in general.