The pool looked just as some black glossy floor in the dark.
We went into the room with a group of other people not related to us and the attendant said something loudly in Greek to everyone as we entered (we obviously could not understand what it was) and just when she finished her little speech I stepped onto the reflective part of the "floor" and found myself in the pool with both of my feet in the water up to my ankles.
This puzzled the attendant a lot because what she was saying loudly to everyone just a second before I walked into the pool was "Please do not step on the reflective part of the floor! It is water. It is just a reflective pool and part of the installation. Please keep away from the water." And the very second she finished the last sentence I walked into the water with quite a bit of a splash. She ran to me and became quite animated talking to me loudly but it was all Greek to me of course. Everyone had a good laugh (at my expense) when it became clear that we were foreigners and could not understand any Greek.
I wanted to buy a pair of dry shoes in the shops nearby after we got out of the museum but they did not have my size, I am too tall and my feet are too big for most Greek shops (and most shops everywhere else too).