In deep water the speed (or velocity) of a water wave depends only on its wave length. Specifically, the speed is proportional to the square root of the wavelength. Thus, the longer the wave length, the faster the wave, or vice versa. The speed of a single wave is called the phase speed. Amazingly, the speed of a packet of waves (the group speed) is often not the same.
Rowing machines were first used in Archaic Greece. Chabrias, an Athenian military general in 4th Century B.C., invented wooden rowing simulators for his inexperienced oarsmen. This enabled them to learn technique and timing before stepping foot on actual water crafts. And it must have worked — Chabrias successfully led numerous naval attacks against the Spartans.
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.