The Challenge AR has the capability to allow the rower to control and adjust the resistance from “Feather light” to “Olympic sprint” delivering a silky smooth resistance to the user’s effort and instantaneous response to input with no “flat sport”.  With water resistance being the most accurate manner in which to simulate actual outdoor rowing, the Challenge AR provides a smooth and consistent sensation throughout the range of motion of the exercise experience.  
Another negative point for me is the angle of the seat. Unlike the Concept2, it has a slight backward angle, which makes it easier to maintain good form at the end of the stroke. Given that the Waterrower has greater resistance at the catch, it puts more pressure on the lower back at this point making it uncomfortable for people like myself with lumbar spine problems.
Function plays a large role in defining good design. When designers look at an object, they don't just consider its aesthetic appearance; they should also challenge it to be more versatile, to respond to the user's need, or to achieve its purpose more elegantly. Good design has the capacity to solve problems that sometimes we didn't even know we had. This is one of the ways design touches and enriches our everyday life.
However, I own an air rower and have zero worries about maxing out it’s ability. I can completely exhaust myself on any type of workout. Air and water rowers are the chosen resistance type by Olympic athletes and any athlete looking to train their full-body cardio. I don’t think they would choose this resistance type if they felt they could max it out.
The water flywheel is comprised of two paddles encased in an enclosed tank of water. As you pull the cable, the paddles move through the water creating resistance. The beauty of this machine is it uses the mass/density of water. The paddles create the drag, so the harder you pull, the more resistance increases. Think about moving your hands through water. The faster you go, the more dense water feels. The slower you go, the less you feel the resistance. And this type of resistance is excellent for your joints. Click here to read the full review.
The WaterRower Classic Rowing Machine is an amazing and long-term investment in your health, as well as the beauty of your home décor. For the money, the durability, quality and guarantee to have a great rowing machine for a very long time. On top of that, this machine provides a level of comfort that will allow you to extend your workouts for an ultimate experience. Highly recommended.
The Classic Rowing Machine is generally quiet for a water resistance machine, but some users believed that it was a little noisy. Like all rowers, whether it’s a flywheel or a waterwheel, there is going to be noise. The more effort that you put into it, the louder it’s going to get. And most find it motivating to hear the water paddles get louder as they burn more calories.
Water rowers feature a tank that is actually filled with water as a means for resistance. As you increase the pace of rowing, the resistance naturally increases as well. This means that you can set your own pace and resistance in a single motion. The same is true for air rowers. Air rowers use a fan or flywheel to create resistance, and you have control over the intensity of the workout due to the fact that the air resistance depends on your pace. Most water and air rowers come equipped with -- or at least have as an option -- monitors that track various functions such as distance, strokes, strokes per minute and calories burned.

The WaterRower Natural is handcrafted from solid Ash wood, finished with a honey oak stain and danish oil. The WaterRower's patented WaterFlywheel has been specifically designed to emulate the dynamics of a boat moving though water and is unsurpassed in its simulation of the physical and physiological benefits of rowing. WaterRower will not provide support or documentation for any product transported outside of the original country of purchase