Well, it’s important if it works — and it probably helps to make your submarine watertight.
The modern submarine is not a simple machine.
A loss of propulsion, unexpected flooding, or trouble with reactors or weapons can doom a sub crew to a watery grave.
Also, it’s a good idea to, like, close the hatches before you dive.
For context, a submarine assigned to Britain’s Royal Navy narrowly avoided a complete reactor meltdown in 2012 after the power sources for its coolant system failed.
That way, you can blame the blue screen of death instead of “human error” for the next critical foul-up. »