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)
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: 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: The dead Royal Navy submarine captain wears a beret. British submarine captains still wear the traditional submarine captain's white-topped peaked cap if they wear headgear at all. His cap badge also features the king's crown, which has not been worn since George VI's death in 1952, instead of the current queen's crown.
Factual error: The Royal Australian Navy special forces operator Wolf Taylor is a 'senior chief'. There is no such rank as senior chief petty officer in the RAN. The two most senior non-commissioned ranks are chief petty officer and warrant officer (the latter a non-commissioned rank and not the same as an American WO).
Continuity mistake: Chandler is reviewing the President's paperwork and finds the manifests which brought his wife and daughters from Washington (document dated 07-05-13) and his son from Detroit (document dated 08-02-13). He then checks the computer for casualty figures in Michigan where the son was originally from (dated 8/4/14-onwards). So the plague hit in early August 2014, but the documents show the family leaving their home a full year earlier. This is not a plot issue (no, they did not fly out a year prior to the plague), but rather a prop-maker error. (00:28:00)