He made the world and created a huge multi-purpose tree to provide food for all.
Sadly, someone had the bright idea of chopping it down so the goodies could be distributed more easily. But for some reason the tree stump was full of water — complete with merrily swimming fish.
This would have been very pleasant except the water was trickling out. Soon it grew to a torrent and threatened to cover the entire Earth.
It was left to SIGU, the son of MAKUNAIMA, to save the world, rescue the animals, preserve ecological diversity, etc etc.
Note: Varying legends claim MAKUNAIMA was not a God but a mortal hero who performed a similar role as SIGU. Like father, like son?