One thing I can't figure out...

We constantly hear about the climate "crisis" and "rising sea levels." However, there's a fort roughly in my home region built on the shore just a few feet above sea level. It's about 500 years old and it's still standing there a few feet above sea level, not underwater. How is that?

(I'm waiting to read that rising levels is a local thing... it might happen in one area of the world but not another.)