Voldemort stood up. Harry could see him now, see the red eyes, the flattened, serpentine face, the pallor of him gleaming slightly in the semidarkness.
But it seems to me that in this semidarkness, amid this liquid that's so dense in comparison to the atmosphere, a gunshot couldn't carry far and would prove fatal only with difficulty!
He took out his wand and gave a great sweeping wave with it; at once, all the candles except those inside the carved pumpkins were extinguished, plunging them into a state of semidarkness.
It was a relief when six o-clock arrived and they could slip out of their sleeping bags, dress in the semidarkness, then creep out into the garden, where they were to meet Hermione and Griphook.