Rowing is a cyclic (or intermittent) form of propulsion such that in the quasi-steady state the motion of the system (the system comprising the rower, the oars, and the boat), is repeated regularly. In order to maintain the steady-state propulsion of the system without either accelerating or decelerating the system, the sum of all the external forces on the system, averaged over the cycle, must be zero. Thus, the average drag (retarding) force on the system must equal the average propulsion force on the system. The drag forces consist of aerodynamic drag on the superstructure of the system (components of the boat situated above the waterline), as well as the hydrodynamic drag on the submerged portion of the system. The propulsion forces are the forward reaction of the water on the oars while in the water. Note also that the oar can be used to provide a drag force (a force acting against the forward motion) when the system is brought to rest.

Ergometer rowing machines (colloquially ergs or ergo) simulate the rowing action and provide a means of training on land when waterborne training is restricted, and of measuring rowing fitness. Ergometers do not simulate the lateral balance challenges, the exact resistance of water, or the exact motions of true rowing including the sweep of the oar handles. For that reason ergometer scores are generally not used as the sole selection criterion for crews (colloquially "ergs don't float"), and technique training is limited to the basic body position and movements. However, this action can still allow a comparable workout to those experienced on the water.

The dense resistance of water creates substantial drag, but on the WaterRower models, this is perfectly tempered by a whippy cord. It coils and recoils with such steady speed that one tester noted how the Classic “eats the rope back up on recovery.” This smooth agility helps balance out the impact of encountering slow water at the start of every stroke.
The WaterRower Natural is hand crafted in solid Ash and stained Honey Oak for consistency of color. Each machine has been hand finished with Danish Oil giving a deep lustre an warmth to the wood. Wood has been chosen due to its marvellous engineering properties, primary amongst these is its ability to absorb sound and vibration enhancing the WaterRower's quietness and smoothness of use.
Storage is also a plus point for the Waterrower series as they are all designed to stand upright with the tank acting as ballast for stability. In this position they only take up around two square feet. Again, great if you are planning on training in the living room. However, if you have small children, I would advise fixing the top to the wall with a hook and strap.
1.) I keep reading about cracks and leaks that develop in the water tank. WaterRower even offers a tank repair kit for this very issue. It seems to me that this is a design flaw that they refuse to address, instead offering a fix for when it eventually occurs. Have you seen these tanks to eventually leak? I’m surprised they haven’t tried a one-piece tank.
The WaterRower, unlike conventional indoor rowing machines, creates a non-impact and non-load bearing environment for cross-training and rehabilitation. The users weight is taken off the knees and ankles by the seated position of the exercise and the use of the unique WaterFlywheel creates an evenly loaded stroke eliminating the heavy jarring and loading experienced on conventional rowing machines, making the WaterRower a popular choice for physiotherapy and sports sciences practices around the world.
Outside of resistance type, we found the number-one arbiter of ride feel to be cord quality. Water ergometers tend to employ nylon cords, while air ergometers feature metal chains — a durability factor we anticipated would result in our favoring air. But while all three water rowers aced our expectation of smooth, high-tension strokes, perfecting the chain seems to be more difficult: Some tug with just a slight rumble, others feature bouncy, grinding chains that are incredibly loud, something akin to angry snoring. As for nylon, the best wind and unwind like elastic silk — no slack, no sound, no catching, just perfectly even tension throughout the stroke.