As part of basic training, all future sailors have got to be able to swim, for obvious reasons. All recruits were required, one by one to jump into the deep end of the swimming pool and demonstrate whether you were a swimmer, or a "sinker" as they called them.
Most of the white guys could swim, dog paddle, or at least tread water. But every black guy in our company, 7 men as I remember, went straight to the bottom, and the lifeguards had to go in to drag them out.
Of course, cities were a lot more segregated back then and I heard somebody speculate that it was because there were more public pools in white neighborhoods than in black neighborhoods, so that may be part of the reason.
I did fine in the Navy swim test even though I never swam in a pool before then. I learned to swim in a lake in a state park. I also was one of four or five out of sixty who qualified with an M-1 at two hundred yards. We were only allowed to fire forty rounds before firing for qualification so I credit the fact that I did qualify to teenage years shooting a .22 to put meat on the table. The M-1 was just another iron sighted rifle but with a heck of a lot more oomph.