One of ours, Bella, will wade in a kiddie pool if it is REALLY hot. She also enjoys chasing water from the hose, etc. But she WAS raised with a black lab puppy as a tiny baby, maybe some of that rubbed off.
I have never tried/asked her to actually swim…I don't know if she would like that.
But I have definitely seen photos of Basenjis happily swimming, and (kind of) retrieving, and boating, and wading. So it IS possible...but I think it is a combination of luck having the rare Basenji that enjoys it, and a lot of opportunity to have postive water experiences (i.e. you live somewhere that it is warm enough that the dog likes to use the water to cool off)