Hi, sorry just saw your comment Princess Mola, Aquafit is simply working out in the water. Each instructor will teach it slightly differently, but often several of the moves will be the same no matter who's teaching, such as jogging or jumping jacks. Both of those would be really hard on a person's knees outside of the water if they had joint problems, but in the water those exercises are able to be done with less pressure on the joints. But even though the exercises are easier on the joints doesn't mean it's not a "real" work-out, it definitely is :-D It's what is called an Aerobic or Cardiovascular work-out becuase it's designed to burn calories by getting your muscles moving and your heart pumping faster than it's normal rate. Aqua-fit is great for people with heart issues as well because while it does get your heart pumping, the temperature of the pool water helps to prevent you from over-heating or putting too much pressure on your circulatory system.
As with any kind of exercise, if you have any health problems, talk with your doctor, but honestly most will agree that Aquafit is a great work-out that's safe for people at many different fitness levels.
I would highly recommend it as a fun way to get into better shape :-D