It seemed like a snap in the water, and Jack could almost imagine he'd heard it, like a crack of sheet lightning hitting the sky. It withdrew and the cave seemed to grow a little darker.

"What happened?" he asked with confusion. "Doctor what happened, what's happening?"

And again he looked down and up again. "The pulses," he said, "they were wrapping around you. Like waves, like brainwaves. Doctor's the creature's still down there, I could see it and it wasn't attacking me. It's like it's waiting."

He was terrified then though, because what was happening? He had no idea. Was the Doctor about to regenerate?

"Doctor are you changing? Is it happening?"