Tai Chi is gentle and makes sure I'm out of bed, out of the house and moving once a week. Also a great instructor, precise but patient and supportive, and a friendly group. One of the few free classes available locally too, part of a Falls Prevention programme.
LullyDully - I was delighted to find a Pranayama Yoga class after a 30 year lapse. Unsurprisingly I am now unable to do many of the postures but benefit from the breathing and stretches. At the end of the class I crawl to a chair to stand up ...
I tried Pilates at a fairly expensive place. 5 or 6 of us in a small room where we had to be careful not to actually touch when we stretched and, unfortunately, a stressed instructor. When I once got cramp and couldn't get up at the end of one class she seemed mainly concerned that I should remove myself before her next class arrived! Such a shame as I'm sure the actual Pilates was really helping my aches and pains. A friend in London goes to a free class in Silk Street which she finds very good. I still do some of the simpler exercises at home.
Must organise myself to swim, sure it would help!