Dog hydro-therapy (or aqua-therapy as it can be called) is suggested by vets all over the world for pets who need to do one of the following:
-recover from an operation by gradually increasing movement and muscle mass without the stress of standing/walking.
-recover from muscular dystrophy (a condition where the muscle have wasted away so the animal finds trouble with or can no longer support themselves). Muscular dystrophy in dogs can be caused by a number of conditions including recovery from surgery and excessive breeding.
-remission from arthritis. While arthritis in dogs will never fully disappear, hydro-therapy has shown great improvements in pain reduction, increased mobility posture.
-obesity treatment. Some dogs and even cats can become so large that normal excersize (running,playing,walking) can actually be harmful for their joints and heart. Aqua therapy with a life jacket is a perfect first step on your pets road to health.