I had a group discussion for my physics class pertaining to Newton's Third Law. My force pair was on rowing a boat. The professor asks me "Much like a rocket or your car, a rowboat propels itself forward by pushing backward on something. Here, that's the water, whereas for the rocket it is its exhaust gases and for the car it is the road. By pushing back on that, there is an equal but opposite force back on the boat to make it accelerate forward. The water should correspondingly accelerate backward, but that's not nearly as obvious to an outside observer. Why might that be the case?

How do I reply to his question?