Rowing is a good idea. If you don't have any actual injuries, just soreness, you can swim with minimal leg involvement. I've done that when recovering from long runs. If you have access to a heated pool it feels sooo good. My gym has a machine called a Krank, which is kind of like moving bike pedals with your arms. You can also take the seat off a regular stationary bike and pedal with your arms from behind. I actually took a spin class where one of the participants was in a wheelchair and did the class that way. She got quite a workout. Where there's a will ,there's a way.