I think of water therapy as something I'm currently involved with right now - exercising in water. I am currently enrolled in a water aerobics class 4 times per week and it has been the greatest aerobic activity I've done in years (second only to soccer in my mind) but much gentler on the body.
I have chronic problems with my back, neck, arms and legs and have found that most forms of exercise, no matter how calmly I go about them, aggravate one or more parts of my body. While I love walking, cycling, urban mushing, and the treadmill, none of these venues has helped me nearly as much as water therapy.
Water therapy is so beneficial because even though you are truly getting a workout (1 hour of water aerobics equals 2 on land), you don't feel it (until you climb out of the pool) and you don't stress muscles, tendons and bones like you do with regular aerobic activity.
The resistance that you get from water is also beneficial to building stronger bones and also developing muscles while toning parts of your body. I am sold on water aerobics and at any level, think it is the 'best' exercise going - especially for anyone over 50.