When we first see the bridge of the submarine, the clock in the background reads 22.47; it then becomes 22.29 after introducing Mo; 23.01 when he talks about being a lucky git; 22.48 on talking about finding immune people; 23.22 when Mo gets up and points his gun; then 23.09 (onto 23.10) when the captain says he's our guest.
When the submarine launches its missiles, someone on the ship says they're going ballistic. An Astute-class submarine is armed with Spearfish torpedoes and Tomahawk Block IV cruise missiles which have a range of roughly 1,000 miles (1,600 km), the exact range is classified, and they aren't ballistic in nature. A Tomahawk launched in the vicinity of the Bahamas at the greater range would cover most of the eastern US and reach into Texas and Oklahoma, but not Phoenix, Salt Lake City or western Europe.
As a Lieutenant Commander in the Royal Navy, Shaun Ramsey makes the mistake of referring another officer who brought the virus on board as the rank of 'Lootenant' as the Americans pronounce, not as 'Leftenant', the correct British pronunciation. Whilst the correct pronunciation of Lieutenant in the Royal Navy is indeed 'Leftenant' it is often spoken as L'tennant or lootenant in more informal situations just as Captain may be pronounced Cap'n.
The Achilles fires 26 missiles in close succession, even if it were possible for the rag-tag crew to upload the labs' coordinates to the individual missiles in that time it would take at least a few hours to fire that many missiles as they would need to keep reloading; Astute-class subs have six torpedo/missile tubes meaning they could only fire six missiles at a time. Even with no safety protocols to slow the process down it would take a significant amount of time. In addition, having fired 26 missiles and 4 torpedoes they would have very few weapons left to do anything more, as they carry a maximum of 38 weapons, typically 19 torpedoes and 19 missiles.
One of the display panels on the British submarine has "meter" spelled the US way.
When the Achilles goes active sonar and gets a target lock on the Nathan James, Chandler orders them to fire three torpedoes down range on the sub's last known bearing. However Ensign Mason said at last contact the Achilles was just under 40 miles distance, making them well out of range of even the Achilles' Spearfish torpedoes, which have a maximum firing range of 29 miles. The Nathan James' torpedo launchers are armed with both Mark 50 and Mark 54 torpedoes, the mark 50 would be the torpedo of choice to use against a small, fast and deep diving sub like the Achilles. The Mark 50 has the longest range of any of the Nathan James' torpedoes, but it is only a maximum firing range of 16,000 yards (9.09 miles). Firing torpedoes at a target just under 40 miles distance would be a waste of munitions.
When the Nathan James goes to Quiet two, all personnel remove their boots to avoid making noise. In multiple shots, after their boots are off, all personnel are shown to be wearing white socks, some with decorative stripes at the top. According to United States Navy Uniform Regulations, Chapter 3, the footnotes state: 'For male and females, socks color shall match service shoes, except khaki socks shall be worn with brown shoes'. In this instance, the socks should have been black.
When the ship is trying to evade the Achilles they go to quiet level two and everyone is told to be silent and not make any noise that might be heard on passive sonar. Then Chandler turns around and orders their helicopter to launch, its true that sound on deck doesn't carry the way it does inside the ship, however the sound of a helicopter taking off could easily be heard on passive sonar. In real life a submarine can even hear a plane or chopper flying at low altitude over the water on passive sonar. Plus a few episodes from now Slattery says that launching a helicopter on open water is too risky because the sub might hear it.
Sean Ramsey states that before the outbreak he was stationed aboard the HMS Achilles as a Coxswain, which is a senior enlisted sailor who is responsible for the steering and navigation of a vessel. Coxswains are always non-commissioned officers (enlisted) and on an Astute-class submarine in the Royal Navy the ship's Coxswain usually held the rank of chief petty officer. Yet when Sean was shown in the flashback he was wearing the rank insignia of an officer, specifically a Lieutenant, and a Coxswain is never an officer.
Ned Hastings tells Niels that they aren't worried about the Nathan James because they are on a submarine. He says "this here is a sub, a destroyer can't touch us, that piece of shit tin can won't even hear us coming." As a former Ensign in the British Royal Navy, Ned should have been well aware that many destroyers, especially an Arleigh Burke-class destroyer, are capable of tracking and destroying submarines. The Nathan James is equipped with state-of-the-art sonar systems and is armed with Mark 54 MAKO Lightweight Torpedoes, which are more than capable of taking out an Astute-class attack submarine like the Achilles.