The episode title "Cry havoc" references "Cry havoc and let slip the dogs of war" as spoken by Mark Antony in Shakespeare's "Julius Caesar" Act 3, Scene 1, line 273.
Sean Ramsey's submarine is described as an 'Astute class'. The Astute class is an actual class of nuclear powered fleet submarine used by the Royal Navy. The lead ship of the class 'HMS Astute' was commissioned in 2010. The 3D renderings of the submarine used in the series are a reasonably accurate portrayal of an Astute class submarine.
Captain Chandler orders the use of non-lethal countermeasures against the American civilian vessels. Lt. Foster indicates she is bringing the LaWS and LRAD systems online. LRAD stands for Long Range Acoustic Device and is used to emit extremely loud sounds to disorient and stun the crew of a surface ship or boarding vessel, depending on the intensity it can disorient a group of people by causing painful ringing in the ears or at full power even cause full unconsciousness, though this setting is used as a last resort because it can cause permanent hearing damage. LaWS stands for Laser Weapons System. It is a directed energy weapon with variable intensity, on low levels the laser can be set to a wide angle and be directed into the eyes of an enemy vessel's crew to temporarily blind and incapacitate them; on high intensity a narrow beam can be used to destroy an enemy vessel's sensors, disable vessel engines, detonate explosives such as mines or missiles and to destroy small aircraft such as UAV's or helicopters. Though as of 2014 (when this series takes place) the LaWS was still in the experimental phase and only equipped on one ship in the fleet for testing: the USS Ponce (LPD-15) an amphibious transport, the testing phase was not completed until 2018. As of 2020 only one US Navy warship is equipped with a LaWS, the USS Arleigh Burke (DDG-51), the first ship of the Arleigh Burke-class fleet of guided missile destroyers. As of 2022 the Navy is planning a $950 million contract to have the LaWS installed on all Flight III configurations of the Arleigh Burke-class destroyers, which are the latest ships in the class consisting of hull numbers DDG-125, 126 & DDG-128-135.
In the background of one bridge scene in Ramsey's submarine a builders plaque showing that it is named 'HMS Achilles' (Her Majesty's Submarine Achilles). While all Astute class boats are given names beginning with A, Achilles isn't one of them. The last Royal Navy vessel to carry the name Achilles was a Frigate HMS Achilles which was sold to the Chilean navy in 1991.