I used to teach water aerobics with all ages. So many of my "students" would tell me how much better they felt the afternoon of and the day after our classes; had more energy and more mobility. It is a proven fact that exercise is good, especially in the water. Our joints have a fluid surrounding them called snovial (sp?);this fluid can get dirty and cause our joints not to work as well. The exercise especially in the water causes this fluid to move around and clean itself.......hence, better feeling joints.