Post Transplant Questions

I am getting back into the pool after a 5 month layoff for a kidney transplant. Perhaps there is someone here who has been through the same process in one form or another. My first workouts are all free for about an half hour and consist of a 50/100/150/200 ladder, with a 200 warm down. I feel good when done, and want to do more; but the Doc's noticed an increase in my creatine level (which measures how well the new kidney is working) the day after the last workout and recommended pushing fluids before, during and after. Now I drink a bunch of water every day ( about 2L ). The question is are there better "fluids" I could use instead of H20?