According to this May 2010 Wall Street Journal story, the USA Swimming 2010 diversity study found that 70% of African American children and 58% of Hispanic children report low to no swim ability.
Since 2007, the USA Swimming Foundation's Make a Splash program has taught basic swimming skills to 325,000 kids. The program gets a lot of support from Team USA Gold Medalist swimmer Cullen Jones, an African-American whose mother made him learn to swim after a near-drowning at age 5.
LOVE Cullen! Here's a recent interview with him:
Cullen's story was told in this 2007 film "Parting the Waters" - check out the synopsis and then the trailer:

Parting the Waters from Louise Rosen on Vimeo.
Not sure where to find the full-length film.
Here's the official website for the film. Not much info there, though - check out this Facebook page for more info.