But the key factor here is that the drag doesn’t increase like the velocity. The drag increases more, this means that when we increase the difference in speed between the boat and the water, the increase in resistance due to the drag goes up more than the increase in speed. This means that the closest we get to WORLD RECORD TIME on the water the harder is to improve speed. This is the reason why it is possible to make rowers fast at the beginning but really hard to win a World rowing championship or the Olympic Games.
Said that what we need to know is that the further we are from World record time, the easier an increase of speed is going to be. This also means that big changes of speed on High school, masters and college rowing are possible but difficult at Elite rowing level.