In addition to this, certain crew members have other titles and roles. In an 8+ the stern pair are responsible for setting the stroke rate and rhythm for the rest of the boat to follow. The middle four (sometimes called the "engine room" or "power house") are usually the less technical, but more powerful rowers in the crew, whilst the bow pair are the more technical and generally regarded as the pair to set up the balance of the boat. They also have most influence on the line the boat steers.
The rowing machine itself is unlike any other on the market with its patented water filled flywheel. It is hard to exactly copy the action of a scull on the water, but the mechanics of the flywheel spinning in water comes in a close second on dry land. The fact that the water is 800 times denser than air means that there is no need for any extra resistance or dampening that you will find in normal air rowers. The faster you pull, the more resistance is generated giving it infinite variability. However, if you want to be able to practice rowing with a faster stroke, you will have to reduce the amount of water in the tank unlike an air rower where you just have to adjust the baffle.