Vesijumppaa

The Hydro Physio Lifestyle Water Resistance Treadmill basically combines "the water resistance of swimming with the monotony of running to create a really strange form of exercise."
The tank is filled and emptied each time which means you can enter through a door on the back, rather than having to climb in which would be problematic for people using the treadmill for rehabilitation purposes. This also means the water level can be adjusted on the fly to allow different muscle groups to be targeted during the exercise routine.