The most convincing explanation is that when someone is finding it difficult to understand what is said to them, he/she engages in a form of lip-reading: he/she will observe the lips of the talker and mimic the talker's lip movements.
Lake Tanganyika is an African Great Lake. It is estimated to be the second largest freshwater lake in the world by volume, and the second deepest, in both cases, after only Lake Baikal in Siberia; it is also the world's longest freshwater lake.
Lake Nyasa is locally known as Lake Malawi in Malawi, and Lago Niassa in Mozambique, is located between Tanzania, Mozambique, and Malawi. It is the second deepest in Africa,with a maximum depth of 2,316 feet and an average depth of 958 feet. It has an area of 11,400 square miles and holds 2,000 cubic miles of water.