Having worked nearly all my life in a job that requires strict climate controls and literally less than 2 miles from the ocean, it’s a problem that is much more complicated than it seems.
Were I a billionaire with a treasure trove of art to protect, I would outfit am inland cave, deep underground, to protect it. Much cheaper, and simpler to do...................
https://en.wikipedia.org/wiki/Isabella_Stewart_Gardner_Museum_theft