There does not seem to be any effect from the water, besides producing a slight chuckle from Jams.
After other member offer suggestions he adds. "Yeah it takes lava jus' fine. We do it sometimes for der holy days and fer extra heat." He even offers to do it himself, as he's experienced. Taking the chalice he tosses the water outside, then fills the cup with lava, before handing it to someone taller for replacing.
The arm shifts slightly down, and a hiss of steam is heard. The wall to the side of the statue slides from view vealing a passage, light by a stream of lava. It turns around a bend about fifty feet down. Gruff voices can be heard from somewhere within, echoing off the walls.
"By the gods. . . " says Jams