Decreasing speed of waves as water becomes shallow has dramatic consequences on the beach. As the waves slow, their profile (Figure on right) is laterally compressed and since each wave must carry the same energy it becomes higher. As the wave approaches shore this process continues until the height exceeds 1/7 th the wave length and the wave becomes unstable. Then the wave breaks.
With magnetic rowing machines, adjusting the resistance means varying the distance between a flywheel and one or more strong magnets. This is done either manually, using mechanical sliders, or digitally by the console controls. Like hydraulic rowers, magnetic rowing machines operate quietly and have a compact design for easy storage. Unlike hydraulic rowers, they can provide a smooth and consistent workout. It's a very different kind of feel to what you'd expect from an air or water rower, though. You still get a good workout, but it doesn't simulate the sensation of rowing in quite the same way.
The horizontal movement of the water when a wave passes is approximately equal to the up and down movement of the water. If you are on flat water and are parallel to waves made by a passing boat, your boat will move side-to-side as much as up-and–down as the wave passes under you. The side-to-side movement actually creates most of the difficulty in balancing the boat in such a situation. However, under typical conditions in the bay there can be such varied wave action that you can’t easily distinguish horizontal and vertical motion.
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.