You are exactly right. Black parents can’t swim and it isn’t a priority that their children swim.
I’ve taught swimming to both races and a fear of the water is what keeps a child from learning to swim, not body fat. You don’t wait until they start to school to expose them to water either. My own children were swimming at three. They “bobbed” around in our arms every summer until they could keep their heads above the water for themselves. They had access to float toys too.
Experience in the water helps the child to excel. Black children are no different from other children when it comes to water.
My mother couldn’t swim but she made sure my brother and I took swim lessons every summer for about 6 years.