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.
If the machine is to be housed on a wooden floor you will need a mat beneath to reduce vibration and also noise. If space is tight, the hydraulic options are usually the smallest. It's also worth checking your floor can take the weight if you're going for one of the bigger, heavier models. For most, this shouldn't be a problem, if you have any doubts get a surveyor to check as it could be a very expensive mistake!
The Water Rower comes partly preassembled in two large boxes. The assembly instructions are reasonably good, and as long as you take your time and follow them carefully (read all the text) it takes about 45 minutes from opening the first box to trying it out. I bought bottles of distilled water to fill it, which made it easy to fill using the included funnel & hose.
The Concept2 Model D is the ultra-popular air rower that you’ll see at most gyms. It is one of the best home indoor rowers you can buy period. Expertly constructed and ergonomically unequaled, this rowing machine looks great and rows smoothly without so much as a jarring catch. As an air rower, the Concept2 employs air baffles to create the resistance. A nickel-plated chain pulls the flywheel and you get your workout by pulling against the increasingly higher air pressure that the fan is creating.
Rowing has long been recognized as the perfect aerobic pursuit, with naturally smooth and flowing movements that don't tax the joints but do boost the heart rate. Now you can take your rowing experience to the next level with the WaterRower Natural rowing machine. Using the same principles that govern the dynamics of a boat in water, the WaterRower Natural is outfitted with a "water flywheel" that consists of two paddles in an enclosed tank of water that provide smooth, quiet resistance, just like the paddles in an actual body of water. As a result, the machine has no moving parts that can wear out over time (even the recoil belt and pulleys don't require lubricating or maintaining). More significantly, the water tank and flywheel create a self-regulating resistance system that eliminates the need for a motor. As with real rowing, when you paddle faster, the increased drag provides more resistance. When you paddle slower, the resistance is less intense. The only limit to how fast you can row is your strength and your ability to overcome drag. And unlike conventional rowing machines, which tend to be jerky and jarring, the WaterRower Natural is remarkably smooth and fluid.