(At around 38:21 min): The Royal Marine pair hold their assault rifles in an unsafe manner. The trigger finger should be outside the trigger guard.
The sonar screen is incorrect; it should be a waterfall pattern, not in a radial scope.
All the Royal Navy personnel on HMS Vigil are wearing radiation monitors yet Amy Silva is not issued one while moving around near the reactor.
It is highly irregular for all submarines communications to be disabled especially SSBNs. They carry back up communications systems or reached by Extremely Low Frequency radio.
At the end, when the captain says goodbye He says "I speak on behalf of the entire ship's company". A sub captain would never call his vessel a ship, a submarine is a boat.