Re: A year into my sobriety.
Wow, congrats on kicking heroin and alcohol and smoking!
I did water aerobics one summer when I was a little older than you. It was a good activity for me!
As for a machine, I don't know what to recommend. I mostly use an elliptical at the gym, which is nice because it's no-impact. I use a Fitbit to track my daily steps and I get around 10-11K a day when I get to the gym (usually about 6,000-7,000 steps I get at the gym).
You can Google for good walking routines but they always recommend common sense and paying attention to how you feel. Start slowly, and build from there. Maybe aim to just get 15-20 minutes of walking in at a time.
If you go for the elliptical, I've found that it always seems very difficult the first day but it seems easier very quickly. So if you try that, just be aware that it will probably never feel as bad as the first time!