I found the answer

[back2dafront]

"Marvin Dunn, a historian and professor of psychology at Florida International University, said that blacks have traditionally had less money to pay for access to swimming lessons and pools. [This is an undemonstrated assertion that is typical of the excuses made for Blacks in every field where their performance is inferior to that of Whites. The fact that somebody named Marvin with the word professor in front his name was willing to say it does not mean that it is correct. This society has bent over backward to make sure that Blacks have at least equal, usually greater opportunities for all sorts of things. There is a physiological reason why Blacks cannot swim as well as Whites. One occasionally hears the unflattering explanation that it is because Whites have more body-fat than Blacks, but today it was pointed out to me that there are plenty of fat Black people. (Funny how one can fail to make simple observations like this.) If body-fat were the key to the racial divide in swimming-ability, then fat Blacks should be good swimmers. I offer this explanation: what is most important in making Whites more buoyant and better able to do the controlled breathing that is necessary in swimming is the larger chest-cavity of White people, which accommodates larger lungs capable of holding more air. Black males also have bones that are 14% denser than those of White males, as well as some bones that are thicker, like the cranium, and this slightly (the skeleton of the average human weighing only 20 pounds) increases the difficulty of staying afloat.]"

http://www.national-socialism.us/archives/week_2004_04_18.html

I've never taken "official" swimming lessons. Several people have attempted to show me how to swim.
I've been shown how to tread water many times but I still can't seem to grasp it. As soon as I start sinking I start freaking out and there goes that breathing technique that's oh-so-essential.

This is interesting though - never knew Whites had larger chest cavities which accommodate larger lungs. This could be useful knowledge when looking for someone to give CPR. :-P

"Grab the white guy - his lungs are HUGE!"

This also explains my inability to take full bong hits. And this whole time I thought my lungs were shot.