There are poses for people of nearly every capability, including many that do not require putting your head down. I even have a dvd for chair yoga.
Walking is great. As for the tummy fat, are you sure your blood sugar levels are staying steady? Insulin resistance and/or type II diabetes are very common causes of excess tummy fat, as is having too high cortisol levels.
Oh I loved water aerobics, but now I don't have a car, and can't get to a swimming pool. You're right, it is great exercise. I miss it. Barb as to yoga, unfortunately I have a problem when I put my head down, I go all dizzy and funny. I tried an aerobics class, and also tried at home, but always this dizzy problem.
I do walk quite a bit, and that keeps me generally fit, but oh this big fat tummy.
You should check on your blood sugar levels to make sure you are using insulin properly. Improper use of insulin can cause a larger than normal tummy.
I agree that water aerobics is great exercise, so if you have a pool available, by all means give it a try. If no pool is available, you might look into some light yoga exercises. Yoga can be great for easing arthritis symptoms.
Water aerobics. The lack of gravity when in a swimming pool will make it feel easy to exercise. My grandmother would go swimming every morning and it helped her keep fit.