How does one hit cannonballs?

I don't understand it at all. I watch all the videos, i practice in HG, and i don't hit anything ever. The ring technique doesnt help me, there's always waves and the cannon itself in the way of me seeing how to adjust my shot, etc. If I use WASD to correct my aim, I correct too much, if I use my mouse, the cannon doesnt move whatsoever. I really want to learn the pvp to this game because I'm good gunplay, but I could never aim myself onto their boat, or put myself at a hole advantage to even begin such a play.