You do it well, then a hard treadmill versus Pure Colon Detox outside are less taxing on your muscles, tendons and bones.
Advantage of swimming over running is that you protects your joints. Did you know that swimming is the least injury-sensitive sports? By the resistance of the water to very quickly build your muscular endurance on. So you can pretty quickly extend the time you swim and so strengthen your fitness and muscle strength. Swim you half an hour, then you already use about 300 calories.