The exercise of rowing relates to the work done to move a boat down a river.
The work done is absorbed by the drag of the moving boat. It is not about resistance.
The more intensively you work, the more drag you overcome and the faster the boat will move.
The limit to how fast the boat will move is you, your physiology, your ability to do and maintain work.
The WaterRowers patented WaterFlywheel design emulates this dynamic but rather than working to move the boat through the water, you are working to move the water past the boat. Otherwise the dynamics are identical.