is your first clue for today's Geo Quiz. Lake Tanganyika is one of central Africa's Great Lakes. It's said to be the second deepest lake in the world after Siberia's Lake Baikal.

Satellite image of Lake Tanganyika

It's a long way from the murky Loch Ness in the highlands of Scotland.

But as reporter Anna Sussman discovered, there's something sinister about Lake Tanganyika, too.

“It's a massive freshwater lake, you'd think it was an ocean when you were looking at it, but its freshwater...and it is home to a massive man-eating crocodile named Gustav. Gustav is a legend he's said to have killed hundreds of people and eaten them, but he's elusive and difficult to find.”

Gustave

Or so the legend says. We'll go looking for Gustav. But first, you need to name the four African countries that surround Lake Tanganyika.

The answers are coming up...