@splitshockvirus >I feel like you could make your backup room design in such a way that it wouldn't matter if it was under water or not.
Yes, but you actually have to design for that.

>Put the generators into a sealed room and have intake and exhaust vented out with a snorkel.
I believe intake and exhaust were already piped, as who wants the basement to fill with carbon monoxide?

You could put each generator in a "bathtub" of sorts that prevents water ingress, with wiring and piping on the roof - although that would makes maintenance a real pain in the ass, as you'd need to undo all wiring and piping and use a crane to remove the generator before you can do maintenance.

>other than for cost reasons
Yes, just like bike shedding, there is sea-wall and generator shedding.

>Or just put them on the roof.
Generators don't last as long when exposed to the elements.

You should really just ensure your reactor doesn't get flooded - designing a high enough sea wall is easier than trying to waterproof generators after all.