A: After writing about the first aerial explorers of the polar regions (Explorers Air Yacht, 1995, and By Airship to the North Pole, Rutgers University Press, 1999), I set off for more tropical climes. I started out to write a comprehensive history of the transoceanic raft expeditions that followed Thor Heyerdahl’s 1947 Kon-Tiki. It wasn’t long before I discovered that there were more than three dozen such expeditions. As an archaeologist who studies the human impulse to explore, it was too good of a challenge to pass by. I was drawn to the almost perfect combinations of science and adventure represented by many of these expeditions.

Also, we have been carpet-bombed these past few years by paeans to Sir Ernest Shackleton (deserved) and upper-middle-class do-nothings wasting money and lives on frivolous mountain adventures (undeserved). I thought it was time for a fun read on serious transoceanic raft adventures.

Q: Who is your intended audience?

A: The intelligent lover of ocean adventure stories. I try to place each of the raft expeditions within the archaeological context in which it was carried out. There is enough science to make these experiments meaningful to the intelligent reader, but not so much as to bore the general reader looking for great sea stories.

Q: How does a raft differ from a sailboat?

A: By its very structure, a raft is a floating warehouse. They were therefore the perfect vessel to carry the contents of a culture across an ocean. They are not fast, but they are virtually indestructible. If a conventional sailboat gets a small hole in its hull, it sinks. By contrast, a balsa-wood raft can lose two thirds of its hull and still keep its crew and twenty tons of cargo afloat.

Q: Did you contact Thor Heyerdahl in connection with this project? Why or why not?

A: I have corresponded with him sporadically since 1979, when I was an 18-year-old adventurer seeking his advice on expedition leadership. I made no attempt to see him personally for this project, though I did correspond with him on several obscure points related to the settlement of Easter Island. I also conducted research at the Kon-Tiki Museum in Oslo, Norway, and was fortunate to be able to interview some of his closest associates, including Norman Baker, Heyerdahl’s navigator and second-in-command on the Ra, Ra II, and Tigris expeditions.

To me, Thor Heyerdahl is an almost mythical figure in world history, a scientist who led some of the most fascinating and important archaeological adventures of the 20th century. I compare him in Sea Drift to his contemporary, the undersea explorer Jacques-Yves Cousteau. Since he is now 86, and embarking on yet another project, I felt it would be too intrusive to bother him personally, especially when so many of the answers I sought were contained in his voluminous writings. In one sense, Sea Drift is in the nature of a tribute to him and the inspiration he has provided to three generations of explorers.

Q: What do you think inspires someone to undertake a journey like those you describe in the book?

A: The example of Thor Heyerdahl, for one thing. There is no question that many of the expeditions described in Sea Drift took their example and in many cases even their rafts themselves from the inspiration of the Kon-Tiki expedition.

Q: What was your favorite story from the book?

A: The American William Willis twice rafted across the Pacific alone, the first time in his 60s, the second time in his 70s. There is one moment, in the middle of his first crossing of the Pacific, when he imagines that a nuclear war has killed everyone on earth except for himself, and that he is drifting across the ocean of a dead planet, the only survivor of the species. That is just terrific stuff.

Q: What voyage struck you as the most bizarre?

A: DeVere Baker's plywood raft voyage from California to Hawaii to "prove" that Mormons had colonied the Pacific. Baker makes a dramatic appearance at the start of the voyage, leaping in front of several television cameras. He was in such a hurry to be off that had put both legs into one leg of his swim trunks, and promptly fell flat on his face. The expedition went downhill from there.

Q: Which trip do you feel was the most successful and which was the biggest disaster?

A: Besides Kon-Tiki, I think Heyerdahl's 1978 Tigris reed boat expedition was a masterpiece, and much under appreciated now. The American Phil Buck carried out another masterpiece when he voyaged from Chile to Easter Island last year in a reed boat.

The biggest disaster? Probably the Spaniard Kitin Muñoz's attempt to recreate the ship carved into statue 263 on Easter Island at the cost of a million dollars. The reed boat lasted only a few days before it broke up and sank.

Q: Were there any other stories you wish you’d been able to fit into the book?

A: No, the book is a comprehensive account of transoceanic raft expeditions from 1947-2000. I have recently learned more details about the expeditions of Eduardo Ingris, but they will have to wait for the second edition!

Q: In researching these voyages, did you find any commonalities that made some successful and others failures?

A: I did not necessarily judge success or failure based solely on whether or not a particular raft crossed an ocean. Rather I judged success based on the successful testing of a well-thought-out scientific idea or hypothesis. The most successful voyages are those that cross the frontier of the imagination and land on some new knowledge of the human experience.

Q: Would you ever think of rafting across the seas yourself? Why or why not?

A: Absolutely, yes. John Haslett, who appears several times in Sea Drift, invited me on the Manteña expedition, but I was unable to go. I hope to accompany Phil Buck on at least a part of his around the world reed boat expedition. But of course my imagination has always been with explorers like Willis or the Frenchman Alain Bombard, who made their voyages alone.

Q: Why, more than 50 years after the original adventure, do you think Kon-Tiki continues to be such a popular book?

A: Kon-Tiki, like Thor Heyerdahl himself, has entered into an area of cultural mythology where we now equate it with the very concept of adventure itself. But I have always believed that adventure for adventure’s sake is ultimately unsatisfying to the human soul. Humans require adventure as a component of our personalities ¾ it is one of the traits that lead us even in childhood to new learning. But the actual triggers of new developments of the human brain, I believe, are the creative combination of adventure with the search for new knowledge. Nearly every expedition described in Sea Drift encompasses this idea pioneered by Thor Heyerdahl that science and adventure seem to be twin pillars of human development. When you take this great adventure and put it into the hands of such a warm and appealing leader like Heyerdahl, it becomes a supreme human experience.