Factual error: 1. Why wasn't Prairie/Masker operating all the time they knew a sub was out there? That's SOP for the US Navy. 2. Spearfish torpedoes are homing torpedoes. They wouldn't just shoot by on each side of the ship, but if they did, they'd turn around and pursue their target until they ran out of fuel. 3. Why didn't the ship employ countermeasures when the sub launched torpedoes? A noisemaker, a nixie - Navy ships don't just cross their fingers and hope the torpedoes miss.
Continuity mistake: While Lieutenant Granderson is being escorted around the compound and walks to the class, she is wearing O-3 rank (two silver bars) on her collar, despite never being promoted during the show to this point. Later on in the episode, when she is talking to her mother, she is wearing O-2 rank (one silver bar) again. (00:13:35 - 00:34:15)
Plot hole: After the nuclear missile has overshot the ship and is determined to be heading for land, a map on a computer display gives an indication of the missile's trajectory relative to the Nathan James and western Europe. After the nuclear detonation, an external shot shows the blast is to the port side of the ship, giving the impression the ship is on a southern bearing off the west coast of France. At the time of detonation, the bridge crew shield their eyes while facing the front of the bridge, which would give the impression the ship is pointed right at the blast rather than off the port side. Later, Master Chief Jeter reports that the jet stream is pushing the radiation north-northeast, as if to indicate the ship is currently sitting in the fallout zone, when this would actually be pushing the radiation cloud away from the Nathan James.
Factual error: Sean says he was the coxswain on HMS Achilles. However, in the previous episode's flashback to the beginning of the red flu outbreak when Achilles was still in operation he was shown wearing lieutenant's rank insignia. The coxswain is the senior rating aboard a Royal Navy submarine and holds the rank of chief petty officer or warrant officer; he is certainly not a commissioned officer.
Factual error: Dr Scott's official personnel record shows that she received her only medical degree, an MD, from Cambridge University. However, British universities do not award an MD as a first medical degree; in Britain, unlike the USA, this is a very prestigious (and rare) postgraduate research degree only awarded to very highly-qualified doctors. The medical qualification degree at Cambridge is an MBBChir (Bachelor of Medicine and Surgery), which is equivalent to an American MD. Although Americans expect doctors to have an MD, it is extremely unlikely that an official personnel record would give false information. The record also shows that her first degree was a BS in chemistry from Oxford. Oxford does not award a BSc degree (as they are called in Britain); most of its undergraduate degrees, even in science, are BAs.
Factual error: Ruskov introduces himself as a vice-admiral. However, he wears the sleeve insignia of an admiral of the fleet, two ranks higher: a wide stripe and four regular stripes (instead of the wide stripe and two regular stripes of a vice-admiral). On his epaulettes he wears the four stars worn by an admiral of the fleet until 1962, instead of the single large star of a modern admiral of the fleet or the two regular stars of a vice-admiral. Given Ruskov, it is inconceivable that he would reduce his own rank or wear the insignia of a higher rank but not use it.
Factual error: The ship sails up the Mississippi river to St Louis. It needs a minimum water depth of 31ft of water. The water depth at St Louis is approx 20ft, so it would run aground. The ship needs 55 meters to clear the mast. Interstate 255 bridge south of St Louis is a fixed bridge with only 27 meters of clearance above the river, so the ship could not pass. Note that New Orleans is the port for Ocean going ships with depths to 200 ft.
Factual error: After the nuclear detonation LT Alisha Granderson reports the ship's fuel reserves as 11% and states they will run out of fuel in less then 6 hours, even at maximum conservation. Working from published specifications (Wikipedia and www.globalsecurity.org) 11% should last them for more than 24 hours operating normally at 20 knots and one would think that maximum conservation extends this timeframe. (00:27:15)
Factual error: They have EOTech or similar holographic sights mounted on their rifles, but "scope in" with a night vision sniper rifle scope of some kind to take out the two targets. The EOTech holographic sights are not night vision, nor have the magnification and reticle that was used in the show. (00:17:50)