"Adele described the pool as a 'baggy old pond' and refused, point blank, to stand in the middle of it. The intention was to fill it with water on the set as she was lifted up on a crane-type mechanism, creating the illusion she was floating on water."

From "ROLLING IN THE DEEP END/Adele cancelled her Las Vegas residency after furious rant over swimming pool stunt" (The Sun). 

She was set up to do a 3-month residency, with "tickets selling for up to £9,000 a ticket." But she didn't like the design for a publicity video.

When you’re a diva, you can do that. You can do anything.

CORRECTION: I thought the design was for a publicity video, but I believe it was the set design, and she didn't want to perform in that environment. That's much less diva, more a realistic expectation for a supportive workplace. The word "stunt" in the headline made me think it was a one-time publicity stunt.