I just want to point out that the border between Northern Ireland and The Republic is in a weird state of legal flux, being sometimes in the sea, sometimes hard

I just want to point out that the border between Northern Ireland and The Republic is in a weird state of legal flux, being sometimes in the sea, sometimes hard, soft, semi-soft, and being a source of violent tension for generations. If you actually go there today you'll often notice nothing at all, but there have been all sorts of plans about what will finally happen once we "get Brexit done".