Wonderful to hear that you have such a great attitude. I didn't know from prevoius posts (prior to this thread) that you have CP. I agree that swimming is in a great activity to help you keep and maintain muscle tone.
Your question seemed to be about whether swimming itself would decrease your siezure activity...that seems to be the unanswerable question, not the question of whether or not you should swim.
I hope my first response did not seem to be too harsh.
Best of luck in your recovery, but most important, keep up the great attitude.