a friend of mine was a swimming instructor, and he is blackI read through all the posts here because I didn't want to repeat this if someone else had already mentioned it. I saw this subject discussed on some program several months ago, and it was being discussed in the context of differences in body structures of races (i.e., Asians are small boned, etc.). White people have a bone structure that results in a longer torso, and it's therefore easier to swim. Blacks have longer legs which puts the naval ("point of balance") higher, and thus are better runners and basketball players. Seriously.
The Takeaway: Black People Better Runners, White People Better Swimmers: Race, Science, and Athletics - The Takeaway
And as a swimming instructor... i will flat tell you that race and or body structure made NO DIFFERENCE in the ability to swim or float.
damn if that don't beat the stereotypes