Watch The Tigris Expedition for Free: How to Stream the Movie Online at 123Movies. . Explorer Thor Heyerdahl and his ten-man crew sailed their reed boat, the Tigris, over routes he believes were followed by Sumerian traders 5,000 years ago. The film goes beyond science to focus on the man, Heyerdahl, in an effort to explain what motivates him to risk his life in the search for knowledge.