When it comes to exercise, water is your friend.
More efficient: The water is more efficient in achieving a total body effect from your exercise. It is easier to work multiple muscle groups simultaneously. Slow functional movements are not hindered by the dominant large muscles, as they are on land, and are more successful in building body awareness. Water pressure helps build up your heart and circulation leading to improved cardiovascular function.
Safer: Exercise in the water puts much less stress on your joints and there is almost no risk of injury due to loss of balance or difficulty with coordination of complex movements. Being safely supported in the water by flotation devices helps you start to regain lost function without fear of re-injury.
Work harder at every level of fitness: Your body has to constantly work against water resistance, and water's ability to cool you lets you work longer or harder without overheating. Best of all, your improving body awareness leads to more efficient body movements that then allow for more intense exercise when desired.
Burn more calories: Constantly using multiple muscle groups to maintain stability, while moving in the water, burns more calories than a similar exercise on land. Your increasing body awareness also allows for more intensity for even more calorie burn over any time period.
Better motivation to exercise: Because of all the above, you work harder in the water than you expect. This positive feedback from water exercising and the general relaxed feeling that comes from just being in the water combine to build motivation to come back for more and achieve your health and fitness goals.