https://model-boats.com/blogs/111166
Quote from blog :-
"The paddling action is produced with a combination of mechanics and software control. A few changes were made to the software to improve the ability to steer. There is still more to be done to improve this. If you watch carefully at 0:35 seconds in the video, you can see the rudder compensating for the paddle stroke to help keep Katie moving in a straight line."
Just for information , some interesting video grabs .
JB