[ikr678]

Off the top of my head: Ocean levels of salt in a water system are much more expensive to maintain (even the secondary loop).

Coastal land much more expensive. If you go to a remote coastal site, you probably won't have as good access to power.

Coastal sites usually exposed to more severe weather events.

Other fun unpredicatble things eg-Diablo Canyon nuclear facility has had issues with debris and jellyfish migration blocking their saltwater cooling intake.

https://www.nbcnews.com/news/world/diablo-canyon-nuclear-pla...

[idiotsecant]

And oysters / mussels / clams / every other creature that starts small and turns calcium into brick finds your cooling system to be a delightful place to raise a family, especially in delicate heat exchangers with small easily blockable passages.