A few days back laminar flow was the word of the day. Turbulent flow is, of course the opposite. Have a look at the linked Wikipedia entry, there’s an amazing amount of information on this seemingly humble object, even jokes from physicists. Rivers exhibit all sorts of turbulent flow as you might expect. Eddies, for example, are a characteristic of turbulent flow.
Paddling does offer its own version of turbulence, although at a scale that I have a hard time seeing as significant. I could be wrong. Paddle design has an effect on how the blade enters the water. Edge conditions and paddling technique offer further opportunities for turbulent flow as the paddle is pulled through the water (or the boat is pulled up to the paddle). The scale of this is in the millimeters in the area around the paddle edge. In the paddling world this doesn’t really pass my smell test. I have a hard time finding any significance in it, although if you ask a racer or possibly a high end manufacturer of racing equipment they might try and convince you otherwise.
Ask them for their data on reducing the Reynold’s Number and see what that shows.