I usually (stopped after op, still not allowed to swim) swim twice a week, I don't work too much so I usually just go, swim a mile or so, then chill in the steam room for 10 mins. I'm not the fastest or best swimmer, but I just pace myself by however I'm feeling, and usually end up swimming a mile in about an hour and 15 mins. Alternate strokes every 4 lengths and I don't seem to have any problems.