Lake Tanganyika contains a sixth of the fresh water in the world! It is the world's longest lake, and the second deepest (the deepest being one is in Siberia, see below).
I went swimming in a lake where it was half a mile deep, and was home to hippos and 10 foot long crocs (we know, ‘cos we saw them!) Whilst neither the depth nor the animals were a problem, I almost got stuck, as a gentle breeze blew the boat away. No keel in traditional dhows means they skim over the water, and the high sides act as a sail! I was swimming hard just to keep up with the boat, and had to "sprint" to get back on board!
The lake is the second largest freshwater lake in the world by volume, and also the second deepest, after Lake Baikal in Siberia (which contains a fifth of all unfrozen fresh water in the world). Lake Tanganyika is also the world's longest freshwater lake, at over 400 miles, and has a mean depth of 570 m and a maximum depth of almost a mile (in the northern basin). It has an average surface temperature of 25 °C and a pH averaging 8.4, making the water in the Mahale showers very soft.