I have had rotator cuff surgery on one shoulder (21 years ago) and labrum surgery on the other (12 years ago). I have paddled/raced surfski and outrigger for years and never had a problem with either shoulder post surgery and rehab. I find that cross training with weights (military press, seated dumbbell press, side lateral raises, front dumbbell raise, upright rows, etc) in addition to body weight exercises (pushups, dips) help strengthen my shoulders and I rarely if ever have any soreness. Good luck!
...Roger