Oh this is the first time I've seen this thread...
My uncle owns an S3 IS. He was taking pictures of me chicken fighting with his kids in the pool just this weekend actually.
This camera's greatest downfall, as well as its star feature, is the MASSIVE zoom capability. Unfortunately this reduces optimal quality output, but the lens still boasts an impressive f/2.7-f/3.5 throughout the range.
Over-exposed images will be super easy to fix, but you should post a few examples so I know just what you are taking about. It is a camera after all. The best way to know what is happening is to look through the internal workings of the camera, out the lens, and see what the camera sees for myself.