I've only been playing Assassin's Creed 3 for a short while. In the beginning, playing as Haytham, you get into a fight on a ship, during which you learn fighting skills such as counter-kill. Animus says to first press "O" (playing on the PS3), then hit the Square button, but, it doesn't seem to work. After pressing "O" I seem to enter slo-mo. Afterwards, I've tried pressing every single button, but nothing happens.
Am I doing something wrong?