Wikipedia
A Rowperfect is an indoor rowing machine designed in 1987; patented in 1988, by Cas Rekers. It is designed to accurately simulate the feeling of rowing on the water. Both the flywheel and the seat are free to move on a slide — this is different from the majority of rowing machines where the flywheel is fixed and only the seat moves. Its mass and movement are balanced and engineered to enable rowing technique to be learned and refined. This is called a "floating head" rowing simulator: the fixed flywheel type is called a "fixed head" ergometer.
The result is that the flywheel moves towards the rower on the recovery mimicking the on-water experience of the boat moving under the rower more accurately. The Rowperfect is also unusual in offering a limited tilt seat which compels the rower to control their weight distribution during the power stroke and recovery. It is considered to be a useful aide to teaching rowing.