For swimming, the norm in America is to think you know how to swim. 80% claim they can swim, but only 56% can demonstrate the five core skills that the Red Cross considers to be basic skills. The skills are (1) step or jump into water that is over your head, (2) return to the surface and float or treat water for one minute, (3) turn around in a full circle and find an exit, (4) swim 25 yards to the exit, and (5) climb out of the water [1].
The author, though, is from Jamaica. I would have guessed that swimming would be much more common there, since it is an island nation. However, to my surprise, a bit of Googling reveals that apparently Jamaicans are no more inclined toward swimming than are those who live nowhere near large bodies of water.
[1] http://www.redcross.org/news/press-release/Red-Cross-Launche...
For baseball: > 60% of the players in the league are White, while 28.53% are Hispanic. That leaves roughly 12% available for Black and Asian players[1]
For basketball: > NBA in 2015 was composed of 74.4 percent black players, 23.3 percent white players, 1.8 percent Latino players, and 0.2 percent Asian players.
In that exactly as many black people play baseball professionally as you'd expect, just looking at population numbers.
[1] http://www.besttickets.com/blog/mlb-players-census/
[2] https://en.wikipedia.org/wiki/Race_and_ethnicity_in_the_NBA