For me, it is cardio exercise, I usually prefer walking or jogging when it comes to exercise.

Walling and swimming are the greatest for keeping you fit without putting undue stress on your joints as jogging or running does. Swimming in a particular is a great exercise for working all the body, arms and legs and everything in-between! Walking particularly with a dog is a great form of exercise, you don't even notice that you are doing any exercise it is such fun!