Instinctively one would expect, that the paddle is pulled backwards through the water during a stroke.
Actually this is not the case – the paddle moves forwards in the water during a stroke! We pull the paddle out of the water forward of the point it was inserted. It might be hard to believe – but you can see it for your self, when you paddle where the surface is covered with alga, brash or similar stuff.
There are two reasons for that; the fact that we stick the paddle in the water flat forward, and glide forward before it “grabs the water”, is one of them. The other reason is the Wing-shape of the paddle; which makes it move like the wing on an aeroplane with the "lift" pulling it forward.
This is quite advantageous as it, among other things, provides us with a longer stroke.
The paddle is moving forward in the water during a stroke. The illustration shows the paddles cross section, and the movement of the paddle, as a seagull would see it; looking from above.