Muschixxl
The reality is that a lot of cabin crew lie on their applications about their ability to swim. Not just in Africa but in Asia too. It is a cultural thing - people don't swim much in some of these countries. Can't tell you how many times I had to fish cabin crew out of a pool.
That being said - to use this as an excuse for not hiring people is pretty pathetic of Kulula/Comair. Many South African companies are forced to give their employees all kinds of extra training to get them competent - due to being forced to hire affirmative action candidates - so I don't see why this airline cannot give a few swimming lessons.