took on water. The crew discovered that a key element of the Egyptian boatbuilding method had been neglected, a tether that acted like a spring to keep the stern high in the water while allowing for flexibility. Water and storms eventually caused it to sag and break apart after sailing more than 6,400 km (4,000 miles). The crew was forced to abandon Ra, some hundred miles (160 km) before the Caribbean islands, and was saved by a yacht. The following year, 1970, a similar vessel, Ra II, was built from Ethiopian papyrus by Bolivian citizens Demetrio, Juan and José Limachi of Lake Titicaca, and likewise set sail across the Atlantic from Morocco, this time with great success. The crew was mostly the same; though Djibrine had been replaced by Kei Ohara from Japan and Madani Ait Ouhanni from Morocco. The boat became lost and was the subject of a United Nations search and rescue mission. The search included international assistance including people as far afield as Loo-Chi Hu of New Zealand. The boat reached Barbados, thus demonstrating that mariners could have dealt with trans-Atlantic voyages by sailing with the Canary Current. The Ra II is now in the Kon-Tiki Museum in Oslo, Norway. The book The Ra Expeditions and the film documentary Ra (1972) were made about the voyages. Apart from the primary aspects of the expedition, Heyerdahl deliberately selected a crew representing a great diversity in race, nationality, religion and political viewpoint in order to demonstrate that, at least on their own little floating island, people could co-operate and live peacefully. Additionally, the expedition took samples of marine pollution and presented its report to the United Nations. Tigris Heyerdahl built yet another reed boat in 1977, Tigris, which was intended to demonstrate that trade and migration could have linked Mesopotamia with the Indus Valley civilization in what is now Pakistan and western India. Tigris was built in Al Qurnah Iraq and sailed with its international crew through the Persian Gulf to Pakistan and made its way into the Red Sea. After about five months at sea and still remaining seaworthy, the Tigris was deliberately burnt in Djibouti on 3 April 1978 as a protest against the wars raging on every side in the Red Sea and Horn of Africa. In his Open Letter to the UN Secretary-General Kurt Waldheim, Heyerdahl explained his reasons: Today we burn our proud ship