HydroHIIT – high intensity interval training in the water –  is a water aerobics exercise class that is enjoyed by both men and women of all ages. No matter the routine led by your instructor, water exercise is safe for the joints. Some people who have had a knee or other kind of surgery find that water is a safe way for them to exercise while they heal from surgery. However, most participants are not under medical care; they simply want to have a safe physical workout so they can stay fit and healthy. People often find they can do things in water they cannot do on a floor. In the water, they feel stronger and more mobile.