Thought I had posted on this? Even if I didn't post on it, I did watch it.
I'm assuming this is in one of those places where there's a liquid with a lower density than water? Anyway, looks cool. If you have the money to stage something like this just for a YouTube video, hey, be my guest.
I believe they're just somehow standing on the under-surface of the ice. So basically they're upside down.

