Long-distance navigator, the paddler Paul Caffyn of New Zealand. Over the past decade or so, Caffyn has circumnavigated Australia, Japan, Great Britain, and his own New Zealand through the low pressure systems of the Tasman Sea in his 17-foot kayak.In a memorable passage in his book, The Dark Side of the Wave, Caffyn is battling a horrible chop off the North Island and sees a fishing boat up ahead. He deliberately paddles away from the boat, fearing that someone on board will see his flimsy craft and ask him where he is going: "I knew they would ask me why I was doing it, and I did not have an answer."

"That is a very hard question," D'Aboville said, when I asked him why he had set out on this seemingly suicidal trip - one of the longest ocean crossings possible, at one of the worst times of the year. He denied that he had any death wish. "And it is not like going over a waterfall in a barrel." He had prepared himself well. His boat was well found. He is an excellent navigator. "Yes, I think I have courage," he said when I asked him point-blank whether he felt he was brave. It was the equivalent, he said, of scaling the north face of a mountain, typically the most difficult ascent. But this lonely four-and-a-half-month ordeal almost ended in his death by drowning, when a severe storm lashed the Oregon-Washington coast as d'Aboville approached it, upside down, in a furious sea. The video of his last few days at sea, taken by a Coast Guard vessel, is so frightening that d'Aboville wiped tears from his eyes watching it with me. "At this time last year I was in the middle of it." He quietly ignored my questions about the 40-foot waves. Clearly upset at the memory, he said, "I do not like to talk about it." "Only an animal does useful things," he said at last, after a long silence. "An animal gets food, finds a place to sleep, tries to keep comfortable. But I wanted to do something that was not useful - not like an animal at all, Something only a human being would do."

The art of it, he was saying - such an effort was as much esthetic as athletic. And that the greatest travel always contains within it the seeds of a spiritual quest, or else what's the point?

The English explorer Apsley Cherry - Garrard would have agreed with this. He went to Antarctica with Scott in the ship Terra Nova and made a six-week crossing of a stretch of Antarctica in 1912, on foot, in the winter, when that polar region is dark all day and night, with a whipping wind and temperature of 80 below. "Polar exploration is at once the cleanest and most isolated way of having a bad time which has been devised" are the first words of his narrative. On this trek, which gave him the title for his book, The Worst Journey in the World, he wrote: "Why do some human beings desire with such urgency to do such things: regardless of the consequences, voluntarily, conscripted by no one but themselves? No one knows. There is a strong urge to conquer the dreadful forces of nature, and perhaps to get consciousness of ourselves, of life, and of the shadowy workings of our human minds. Physical capacity is the only limit. I have tried to tell how, and when, and where. But why? That is a mystery."

Paul Theroux