Have you noticed that every swimming race in the China Olympics has been a world record? Some people might jump to the idea that all the swimmers are juiced. Given how many times that Michael Phelps was tested for drugs I find this highly unlikely - although it is just a matter of time until a French newspaper makes the claim.
Could there be something in the water? I'm not typically a conspiracy theorist but China is very motivated to show well in these games. Could they do something to the water that would allow the swimmers go faster? Could they reduce the friction or something? Just a random thought.