No, you didn't get it at all.
It's like how humans are instinctively wary of spiders and snakes. It's a genetic trait that pretty much kept us alive for millions of years, and while not everybody is downright phobic about it, all sorts of creepy crawlies is still a "nope" thing to 99% of the population.
In the forests of Europe, staying in the water is a good idea - you might catch a fish or cross a river, and then later when you're boating around and you fall into it - you survive.
On the plains of Africa, or anywhere there's black people due to hot and humid sunny climates, staying out of water is a good idea and people who instinctively avoid water survive in greater numbers.
Hence it's not that blacks lack the ability to swim or learn to swim, but they don't like to. It just doesn't come to them to think, "hey, let's go out on the beach and spend a day jumping in water" beause that sort of thinking got their great-great-great-great-great... cousins killed.