Same reason they don’t surf or swim— atavistic memories from the slave ships and the “sharks that still follow the course of the slave ships, even today” (some idiot congressman posited this ridiculous notion). LOL.
If you’re camping in lion country you need a kraal of thornbushes, around the camp.
Swimming in african rivers— not generally recommended, black or white, as the crocodiles make no distinction for supper.
I always heard crocodiles preferred the dark meat.
The density of the bones in the Negroid race, along with lack of sub-cutaneous body fat makes it very difficult for blacks to float. On the other hand, women have more sub-cutaneous fat, and the bones are less dense, making them the most likely to float, so more likely to have lack of fear to learn how to. Floating is the first thing a person learning to swim must do to feel comfortable in the water.
There are several programs in Denver that take inner city youths into the mountains to hike or ski. Generally, they love it, but just can't afford to do it on their own.
They do go on cruise ships, so they’ve overcome that atavistic memory.
I am trying to think of some things that Americans of northern European ancestry got hard-wired to avoid over the generations.