Lake Tanganyika is a staggering geological feature, a flooded rift valley occupying the southern end of the Western Rift Valley and forming the boundary between Tanzania and Congo (Kinshasa). The basin formed nearly 25 million years ago when a block of the Earth's crust dropped down leaving blocks on either side and creating the deep chasm in the western arm of Africa's Great Rift.

Lake Tanganyika is less of a lake and more like an inland sea. Even the creatures found here seem like ocean species: sponges, crabs, jellyfish. The lake's sheer size - and the length of time it's been isolated from the outside world - have led to the evolution of creatures such as Limnonida - similar to ocean jellyfish, yet totally unrelated.

After the lake was newly formed 12 million years ago, a few fish invaders arrived - probably up the Congo River. They were simple cichlids. Their descendants have come to dominate this lake, over a hundred new species of cichlids have evolved from those first invaders, and they've spread into every conceivable nook and cranny.

Today the lake supports a thriving fishing industry sustaining an annual catch of close to 50,000 tonnes. There are more than enough fish in this remarkable lake to feed all the people who live along its shores - perhaps even enough to feed all of Africa.