Silent Pool

The  was a lake near the Eddison Manor in England. On 8 December, 1926, Agatha Christie, the Tenth Doctor and Donna Noble drowned the Vespiform Reverend Arnold Golightly in this lake. The next day, Agatha's car was found by the side of the lake. (TV: The Unicorn and the Wasp)

Behind the scenes
The name of the lake is not mentioned in-story, but its name is on a sign.