growing your body optimized for swimming. The training is one thing. I mean shaping your body into the hydrodynamically optimized form, like say growing some muscles (or fat - shaping yourself into a more dolhpin like shape :) here and there mostly for the purpose of better resulting hydrodynamic shape. With the medicine advances it may start earlier in life and be non-catchable by the sports authorities.

And, if you look at one of the Chinese Olympic winners last year - the wave in front of him was significantly smaller than in front of anybody else. Have no idea how he achieved that though.