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.
At more than 25 million years old, it is the oldest lake in the world. Lake Titicaca is a lake located on the border of Bolivia and Peru. It sits 3,812 m (12,500 ft) above sea level making it the highest commercially navigable lake in the world. By volume of water it is also the largest lake in South America.