You probably rode the ride when the sound was off or out of sync, that's usually an overnight fix, sometimes if its really bad they stop any more guests from loading and turn them away (Has happened to me twice). Overall you hear the dead man tell no tales narration right before the projection as many have stated.
You had a bad ride through, happens sadly but nothing to get too worried over, unless of course this issue with the audio stays the same. The mermaid effects make me extremely disappointed and mad, I like the addition of the song. But really the projection effects are terrible and hardly work, nearly every time I have ridden the ride one or the other projection system isn't working. Not to mention it's so quick and poorly done/looking its hardly anything to gaze at. I think a simple tail animatronic flicking out of the water would have worked much better.