The moment he started about “containing the heat inside” I was like doubt, it would be a miracle material used in everything if it did that (aka us mere mortals can’t afford it for something like a swimming pool)
I was fully ready to believe that a vantablack pool would boil in direct sunlight. Not flash boil, but I excused that as the author being a bit enthusiastic.
Wasn't till the nuke that I was acting ready to call bullshit. The chlorine gas thing felt wrong, but I don't know enough about chemistry to be confident that flash boiling chlorinated water wouldn't produce chlorine gas at possibly lethal levels.