Fascinating, seems kind of like a water-bound analogue to the omni-directional wheels used on forklifts and such ( e.g. https://www.youtube.com/watch?v=0DBXuZv38l8 )

This was definitely required to help me figure out what the heck is going on. Basically it's a water wheel on its side, where the angle of attack for your paddles varies, which allows you to direct thrust in a particular direction.