If you can afford a 100+ million dollar yacht you can afford a climate controlled art gallery on board.
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...................