Faked cannon test in episode 1?

I just got through watching episode 1 where they are testing the Archimedes cannon.

If you watch it closely (or frame by frame) the cannon shot clearly goes into the water. You can even see the splash in the next cut-scene. They tried to do some good editing, but you can see the trajectory go into the water and a splash of the water where it landed.

Next, they show the cannon ball going through the hull. If go frame by frame here, you can see the wadding behind the cannon ball come through the hull. Whereas in the previous clip, you can see the wadding fall way behind the ball. This leads me to believe they put the cannon directly on the hull of the ship and fired it to give it the appearance that it went through.

Finally, they added an explosion (detcord? + some gasoline) to make it look like it was doing some real damage.

I can understand if they had some difficulties and could not get it to work, but they should have stated that instead of trying to fool us into believing that what they did actually worked that way.

Do you agree?