As a boy growing up in Norway, Thor Heyerdahl was afraid to swim. As a young man, he crossed the Pacific on a balsa raft called Kon-Tiki. In his middle age, he sailed across the Atlantic in a ship made of reeds.

Now he is 66 and still thinking of places to go, of questions to be answered.

"All my life, if I wanted to do something, I was never satisfied by just dreaming about it. I wanted to do it."

The boy who was afraid to swim grew up to be an explorer, an archeologist, a best-selling author and film-maker, a scientist who studies the origins of primitive cultures -- but above all a man who did the things that other people merely dream of.

Heyerdahl is still fielding requests from people who want to share in his adventures. They send him letters; they approach him on the street. Recently he was at the Academy of Natural Sciences in Philadelphia to give a speech on early man and the ocean. At a pre-speech lunch, a scientist asked to join him on the next expedition.

But he chooses his companions carefully. "One thing is very important on an expedition. You have to, of course, be physically strong and healthy. But also you have to have a sense of humor. You're going to live together for months on a little boat. If you are a fanatically political or religious fellow, the you don't match with the rest of the group. That's a very important thing, human character."

What made Heyerdahl an explorer? "That was an inclination from before I started school. It has always been in my blood. I suppose part of it might theoretically stem from the fact that Norwegians are very interested in seeing other parts of the world. We saw that in the Viking era and we see it also in modern times. We are a tiny nation and we have one of the largest merchant marine fleets in the world.

"But I think primarily it was my mother. She was tremendously interested in science and before I could read, she would show me big, heavy volumes with pictures of primitive tribes or animals. She was fascinated by Darwin.

"My father was president of a bank and of a brewery. And I can still very clearly remember -- I must have been 14 or something -- the last time he asked me, 'Are you absolutely sure that you want to become an explorer? Because in that case, I want to dispose of all my business and there will be no possibility for you to take over later.' And I said, 'I am 100 percent sure. You can tell the brewery that I couldn't care less.' I have never regretted that for a moment."

The ocean was always alluring. He was born and raised in a small town called Larvik, about an hour's drive from Oslo. "Our house was on a hill overlooking a small fiord, the Larvik fiord, which flows into the Oslo fiord. oAnd I remember particularly in the summer months -- when it was daylight very late and I was put to bed very early -- as soon as my parents had gone downstairs, I jumped out of bed and climbed up and sat in the window. It was one of those old, white-painted wooden houses. The window was on the second floor and I could see the whole fiord and also see the land disappear, the hills and forests on both sides, and the open ocean beyond. I was always dreaming of getting out there and going far away and seeing the world."

The ocean could also be ominous. "Very often, in wintertime or in the dark autumn with storms whipping up the breakers on the rocks, I dreaded it. I thought it was horrible and I was dead scared of the ocean. I was so afraid that my father's greatest worry was that all my friends swam and he couldn't get me into the sea.

"But that's the way the ocean looks from the shore. Now, when I learned to see it from mid-ocean, where you have the long rollers or even in a storm, I've learned to love it. I'm very fond of the ocean."

For the past 22 years, Heyerdahl has lived in a converted monastery overlooking the Italian Riviera. Like his boyhood home, it is also a place with a view. "I live in a medieval village surrounded by farmers with my own donkeys and goats and animals and my own olives and grapes. When I left, the oranges were just ripening in my garden.

From my window, I can see the whole Mediterranean, right down to Corsica in one direction and in the other direction, I can see the snow on the Alps. When I'm looking at the ocean there are moments when I can visualize the early Roman vessels passing by or Etruscans or whatever it would be. I can see, particularly in the evening, the lights from the torches of the fishermen out there and I can hear their voices although I am 700 feet above water level. I have water around me on three sides. It's a peninsula and I have the whole top of the cape."

When he is home, his days are devoted to work and to answering mail. A hundred letters a week from all over the world. The letters from scientists, autograph seekers, would-be explorers, people with a cause. In the past decade, Heyerdahl has traveled to 23 countries in a campaign to alert people to the dangers of ocean pollution. "All sorts of people write to me for help in campaigns to protect the whale and the seal in the Arctic or for anti-pollution or to contact the shipowners of the world for this and that or scientists, for international collaboration, they want me to help with this and that.

"I have a very rigid working time. I get up at 6 in the morning -- I love to get up in the morning -- and by 7 I have had my breakfast and a little run or a little walk in my own forest. And then I sit down and work." He works in an old Roman watch tower a few steps from the house. "By 5 or so in the afternoon, I cut off and then go off into my own forest or on my own land and do physical work because I need it. Otherwise I feel unfit and unhappy. So then I work until I really perspire. It may be breaking or carrying stones or it might be clearing underbrush to prevent forest fires or planting or any heavy work, digging trenches or anything like that.

In respect to his age Heyerdahl said, "the only thing is, I cannot run as fast as I could before but I can run as long and I can take lifts and turns as heavy. I am very healthy."

Retirement is out of the question. Although he is not planning any raft expeditions in the forseeable future, he is working hard on an archeological study of how the first civilizations developed 5,000 years ago. "The first question I get from any journalist when I step ashore from any expedition isn't 'How was it?' but it is 'What are you going to do next?'" But he will not undertake an expedition unless it will provide the answer to a question. "If there is any reason for doing something, I will do it, but I wouldn't go on an expedition just for the sake of sitting on a raft. There has to be a point to it."

These days, the biggest threats to his expedition come not from nature, but from man. Political problems. "This is something which is getting worse and worse. Places where I have organized my expeditions one by one are getting eliminated. For instance, a while ago, I went into Chad and I almost lost my head there but today you can't get in there at all. The area where I went into to get my boat builders for Ra I and the whole area where I sailed on the Tigris -- Iraq, Iran, the Gulf -- that whole area is now a prohibited area."

The Tigris expedition, his last trip, was in 1977. "All along Somalia, there was a war raging. We heard the sound of guns and planes over us, but we were not permitted to go ashore. So we had modern problems that ancient man didn't have."

Heyerdahl said the most frightening experience he ever had was when the Kon Tiki -- after drifting for 101 days with the wind and the current -- was thrown up on the reefs in the Tuamotu Islands on the windward side. "The surf was higher than the top of the mast. And on sharp coral reefs. And at that time I really thought this was the end of all of us. It was an unforgettable moment. We were washed up and washed out again 12 times until we were thrown so far up that the raft got stuck on the reef and we could jump out and wade in to an uninhabited island," he said.

Afterwards, he felt immense relief. "After 101 days, to walk barefoot ashore on the warm sand and see the palm trees overhead is just like paradise. You fall down on your knees and grab the warm, dry sand in your fingers. It's an experience that repays all the suffering."

There is paradise in mid-ocean as well. "You feel a part of the universe. You have the sky with the stars and the sea with the plankton and that's all. You wake up; in a sense, you live. You feel it right through your brain and your body that this is reality. When you come back and live the life of modern man, it isn't reality. It isn't the real thing. We've forgotten the truth about life the way we live today." life of modern man, it isn't reality. It isn't the real thing. We've