Factual error: No ship has ever been - or ever will be built without having emergency fuel shutoff devices that can be manually operated.
Factual error: In one scene they attempt to divert the ship by manually activating the ship's bowthruster. A thruster is a propeller in a transverse direction. This allows the ship to turn more efficiently when docking. However the thruster loses any efficiency above approximately 5 knots. In the film they use it at 17 knots. Secondly, a thruster is powered by an electric motor of at least 500 kW, yet they manage to turn it by hand. That handle does not exist in real life, and no one would be able to turn it anyway.
Factual error: You cannot walk into a ballast tank from the accommodation areas. The tanks are not painted white on the inside, and electric lights are not installed in ballasttanks. And finally, when filling ballasttanks, it is done through a pipe and a pump, not by opening gigantic doors in the ship's hull.
Continuity mistake: You have to look really close, but while they are dancing, when the alarms go off, Sandra Bullock is wearing hose. Later, when they are running around the ship, she has taken them off. Then towards the end, wear she is under water, with her hands tied together, she is wearing pantyhose again.
Continuity mistake: Throughout the movie, the cameras show a wide shot of the cruise liner from the sky, the evening before all the commotion look for the name of the ship, it is painted over, but the next morning, the name is perfectly readable.
Factual error: Near the end, the starboard anchor runs out, into a car on the pier. The anchor chain on a normal vessel of that size is about 300 meters long, and fastened to the vessel at the end, in the bottom of the so-called chain-locker. And the anchor does not come out of the ship in a roll lead, it has its own opening in the hull.
Continuity mistake: On the bridge the speed is shown going down fairly fast. The camera shows it going down from 17.8kts to 17.3kts. Geiger is then made aware of the deceleration and opens up his PC. The speed is still decreasing but is only at 17.1kts when he first looks. The speed is still going down at the same rate so should be well past 17.1kts on Geiger's screen.
Continuity mistake: When Annie is being taken hostage at the end, Alex jumps down onto the stern door but misses and lands in the water. He is then shown hanging onto the stern door's edge. Since the edge is about 10 feet over the water's surface, he must be a pretty good athlete to jump and grab hold of it.