His swim skill will probably be lower than Michael or Trevors, but he'll definitely be able to swim.
Not really racist, just logical. The player skills are: Special, Stamina, Shooting, Strength, Stealth, Flying, Driving, Mechanic, and Lung Capacity. Franklin will likely have a lower Lung Capacity rating b/c a much larger percentage of people who live in the inner city don't know how to swim (or swim well) when compared to people from suburban or rural areas; and we've yet to hear anything about Franklin's character that would alter that assumption. It's not any different than the fact that Franklin will also have a higher Driving rating than Trevor or Michael because he is a more experienced driver though his work as a Repo Man. Each character will have skill ratings justified by the type of life they've lead.
Note to GFAQs mods: You do an absolutely terrible job at modding trolling. Get better at it and give harsher punishments for it.