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.
Largest lakes by continent. The largest lakes (surface area) by continent are: 1  Australia \ Oceania - Lake Eyre (Salt lake) when filled; the largest permanent and freshwater lake in Oceania is Lake Taupo.  Africa - Lake Victoria, also the third-largest freshwater lake on Earth. It is one of the Great Lakes of Africa.