Having the unguessed countries the same colour as the lakes makes it harder. I totally thought the lake was just that big and wondered where the hell I could fit in a country!
On every other official points status quiz on JetPunk land borders don't count. Even the man-made customs island border between Saudi Arabia and Bahrain usually gets disqualified. And bridge borders like Singapore and Malaysia are completely thrown out.
No, it's a lake so it gets split into the four countries. Zambia only controls the far south west corner of Lake Tanganyika. Here's a map to show you the borders