Aquatic rehabilitation is rapidly growing in the field of physical therapy.
Warm water has many properties that provide rehabilitation for people that suffer with disabilities and chronic pain. They include:

Buoyancy which lessens the effects of gravity thus reducing the load on the bodies' joints and thus reducing pain.

Hydrostatic Pressure which decreases swelling and the tendency of blood pooling in the lower extremities. It also helps to strengthen respiratory muscles.

Friction which provides resistance to movements, thus creating an excellent environment for strengthening all muscles of the body. As the body moves faster in the water the resistance increases. We often add equipment to arms and legs which adds more resistance and intensity to the exercise.

The aquatic environment increases range of motion, which increases muscle strength, endurance, and overall functional mobility.