East Africa - Mouth of Zambesi - Wide stretch of river , boats beached on sand. Part of Box 249 Boswell Collection - East Coast of Africa. The Zambezi (also spelled Zambeze and Zambesi) is the fourth-longest river in Africa, the longest east flowing river in Africa and the largest flowing into the Indian Ocean from Africa. The area of its basin is 1,390,000 square kilometres (540,000 sq mi)