All large modern merchant vessels nowadays are fitted with two independent parallel bilge systems, a Daily Bilge system, for daily leaks and drips, and a Rule Bilge system to meet classification standards and is sized by compartment size, pump capacity and equipment in the spaces.
Every watertight compartment will contain a bilge well in each corner of the compartment, each containing a multi-stage alarm sensor with a Low Level alarm and a High Level alarm. These alarms are shown in the Engine Control Room, ECR, and repeated on the bridge, both spaces are manned 24/7. Usually the Ballast System can also be crossed over to the Rule Bilge system for additional capacity and also, in main propulsion spaces, there will be an Emergency Bilge suction connected to the largest capacity pump, usually the Main Sea Water pump. The Rule Bilge system will have a direct overboard valve that can only be opened on authority of the Master, plus the Main Sea Water Pump will be directly overboard.
That is the arrangement on a merchant ship, I would fully expect a warship to have higher levels of detection and redundancy. None of this is negotiable, it is all clearly laid down in Classification Society Building regulations and monitored closely by them during the build process. Cost is not a factor.
All bilge alarms should be attended to, by sight, as a priority to maintain a clear panel and an immediate and obvious warning. If equipment that has the potential to either cause flooding or to compromise the bilge system is out of commission then additional watchkeeping manpower should be used to protect the space.
Flooding of a compartment to a level whereby electrical equipment is damaged simply cannot happen if all equipment is being used as designed. If a main is temporarily broken for maintenance the end should have a temporary blank flange fitted. If the bilge system is down then alternative temporary arrangements should have been in place.
Allowing for the fact that the media will have completely changed the facts for the sake of a story the fact remains that, in this day and age, the flooding of a compartment simply should not happen and I would be very surprised if anyone can come up with a creative scenario to justify an ‘Unavoidable Accident’.
And yes, one fire pump will be designated as an emergency pump and will automatically start on reduction of system pressure. That way, in case of fire, all you need to do is open a hydrant and the pump will start up. Further pumps can then be manually put on line depending on the number of hydrants in use.