Continuity mistake: When the stairs are first shown, there's carpet up the middle of the stairs. At the end when they flee the house it's gone.
Visible crew/equipment: Young vampire Danny floats away from the window after being confronted with a crucifix. The effect is quickly ruined when the boom he is sitting on can be seen moving him for 8 seconds. (01:43:40)
Factual error: When Brian fires a rifle at the shark from the boat, he fires the rifle multiple times very quickly. The rifle he is using is a bolt action rifle, which must have a bolt part moved before each fire. He does not touch the bolt.
Continuity mistake: When Watson is conned by the prostitute who says she knows Mary Kelly, she lures him into a closed alley. After Watson has called the police and subdued the attacker, 2 constables arrive and arrest Watson, but as they all leave, a third constable comes from behind the camera. Either he magically appeared, or he walked through the wall behind.