At first glance, the water therapy class in the Parks and Recreation swimming pool might look like a group of people just standing around in the water. But, like ducks on a pond, there's much more going on beneath the surface.

Every joint from head to toe is being exercised during the class, offering a low-impact workout for participants and providing relief from the effects of arthritis.

Around 32.5 million adults in the United States suffer from some form of osteoarthritis, the most common arthritic condition, according to the Centers for Disease Control and Prevention. Physicians recomme...