If you are no longer getting a kick out of swimming, I suggest you try a rocking group class like kickboxing. Your upper body will still take a beating (bad pun, I know), but you will be working your shoulders in a wider variety of motions, which is great for injury prevention. Jumping around on land is good for your bones since it's weight bearing, unlike swimming. Plus, being in a group class can buoy your waning motivation. The loud music and fun moves of kickboxing are certainly different but still complementary to your time in the pool.
If you're game to try, here's more on Cardio Thai Boxing.