User blog comment:Miskos3/Fairy Tail Episode 256: Tartaros arc: The Final Duels, Review/@comment-25111584-20151024095646/@comment-7418318-20151024101313

Regarding the water:

Don't forget that this water-silo (or whatever it was) ruptrued there, enabling Lucy to have a surf-battle with the small-fry. There's bound to be some of that water around still.

And Juvia also fought there, which would probobably also leave a few puddles behind.

So even with Aquarius' and Torafusa's respective waters disappearing along with them, there's still plenty of "real" water around for this scene to be possible.