Other mistake: The way Sid interacts with the whale's blowhole is illogical in relation with the manner the water is being discharged. When viewing Sid up close, it is seen that the water stream is divided and outspread due to Sid's manner of blocking parts of the blowhole with his body. Despite that, when viewed further away the water stream is intact and traveling straight ahead. Once the water stream is seen doing just that, the following shot shows a boar getting hit by it as if it somehow hadn't already occurred, not only that, but the stream of water that was displayed in that shot was delimited, despite the water discharge never being paused and Sid never changing positions. When Sid starts rotating, delimited streams of water are seen traveling in various directions one at a time, when there should have been multiples at a time according to what is viewed when close to Sid. (01:07:05)
Other mistake: The news anchor in the opening scene noticeably flubs her lines at one point.
Other mistake: When Steve, wearing his improvised shark cage, heads underwater to turn off a relay to prevent the others from being electrocuted by a falling wire, he is shown breathing through a snorkel taped to several metres of hose, open at the surface end. In reality, human lungs can't expand enough to pull fresh air through more than a couple of feet of hose. That's why diving hookahs use an air pump to feed air from the surface to the regulator mouthpiece.
Other mistake: After the daughter visited with her mother for the first time, she is reviewing the footage with the priests. No such camera angles were taken for what they reviewed, only an overhead room camera would have been available.
Other mistake: Cam says he ran for fifth grade class president on a platform of getting rid of a dangerous playground slide. Marty later says he voted for him, but that he was in fourth grade at the time, which would have made him ineligible to vote.
Other mistake: Throughout the saga, blood has been shown as essential for vampire's healing factor, and Selene herself used her blood to heal people. Somehow, this time around neither her or her pal David think in any way of this basic fact, making a complicated trip to the vampire doctor necessary, who simply feeds the vampire kid some blood, the very first thing any vampire would do to regain strength.