Continuity mistake: When Doyle arrives at the dock at the beginning of the movie, we see Doyle from behind. A boy with a yellow shirt and a girl with a flower dress pass him on his right side. However, there is a change of shot, and now we see him from the front, and behind him we see the boy and the girl, but instead of being at his right side, they're at his left.
Revealing mistake: When the black guy is attacked after being let go, his throat is slashed. Check out how dreadfully fake the blood is. It looks like watered down ketchup.