Silly silly there are no sharks in the rivers,,, They are afraid of the crocodiles.
So I'm going to get on a prey animal, ride it through lion country dodging black mambas, cobras, monkeys, pissed off tribesmen, every plague carriing insect in the world, wade across crocodile infested waters, then swim in an area known for Great Whites? This sounds like one of these,,, "Hold my beer" moments.