Swimming is awesome cardio bro. I wish my gym had a pool. Its getting pretty close to a workout I think as well, my shoulders always tire when swimming. I would keep intensity as light as you can when doing it.
Same shit though, swimming after an arm and or shoulder day is the same thing as running after a heavy squat day. Sometimes is feels as though you are hindering recovery. I prefer to do real life cardio, like mountain biking or swiming etc over hitting a treadmill. Its not so bad though if there is something good on TV, or I have some good tunes in the Mp3 player, and some hot scenery at the gym. lol
Mavy