The river Nile is ~ possibly ~ the longest river in the World. It flows roughly from the south to the north through ten countries in Africa ~ eventually draining into the Mediterranean Sea at Alexandria ~ just north of Cairo ~ in Egypt. The actual source of the river has not yet been definitely located ~ hence the word 'possibly' in the opening sentence. One day explorers in Rwanda or Burundi will decide this matter. Alternatively there are tributary rivers that flow into Lake Victoria in Tanzania. Tracing the origins of rivers feeding into the Lake is not easy in thick mountainous jungle terrain. Some of the countries are war-torn, and visitors need to seek good advice before planning travel.
If travelling upstream from Khartoum ~ in the Sudan ~ the Nile splits into two. The Blue Nile joins from the east, the White Nile runs mainly south-north.
I have read of several modern adventures on the Nile. One concerned kayakers paddling some horrendous rapids, with whirlpools big enough to swallow ships. They carried suba-equipment in case of capsize ~ and even had a helicopter flying overhead to assist with rescue. (Yes, I believe it was required!). The calmer stretches do not appeal to me either ~ Nile crocodiles are plentiful, hungry, and no match for kayak. I leave it to readers to find out more ~ there is an abundance of facts and pictures on the WWW. Wikipedia is always a good place to start.