I then learned why we can't have nice things. The Tigris, another reed boat, was Heyerdahl's final voyage, in 1977. It was intended to prove that trade by sea would have been possible between Mesopotamia and the Indus Valley (now India and Pakistan). During this voyage, the Tigris was turned away from entering the Red Sea by military vessels. Forced to land in neutral Djibouti, Heyerdahl intentionally set the Tigris on fire as a protest against war. Heyerdahl never again sailed, and spent the rest of his life as a peace and environmental activist.