Doctor Who: 10 Terrifying Moments In Under The Lake
6. Pritchard's Death
Poor Pritchard, the company stoge; he goes out into the water in search of valuable salvage believing that he has hours of 'day mode' left. So when he returns through the airlock, he doesn't expect the two ghosts to be waiting for him.
In the most chilling part of the episode yet, they activate the controls to open the airlock and flush him out into the lake, killing him. What makes it so terrifying is that there is no one there to help him and nothing he can do to stop it. All he can do is watch the spectres through the glass as water fills the chamber.