Arthritis, and other musculoskeletal problems put me on the disabled list a long time ago. So, if I want anything resembling sustained cardio, it’s water or jerking off. Or both, I guess.
Point being that water based exercise is a wonderful thing when you have any kind of mobility issues. You get resistance without stress on joints, or at least a lot less stress. So you can bust your ass and get some good work in instead of doing fifteen minutes and needing a handful of NSAIDs and the rest of the day to recover.
I just wish I could go more often. We don’t have a pool in our town that’s even semi useful for that. The YMCA the next town over has times set aside, but it’s a tough thing to schedule in.