Doctor Who: 10 Most Terrifying NuWho Monsters
5. The Flood (Waters Of Mars)
It only takes a single drop.
Born from a mysterious life form that takes over the host body, the Flood transforms all biological life containing water into lethal zombies.
Imbued with the ability to spray an endless supply of water, the danger comes from the fact that it only takes a single drop to change the individual into a walking ocean.
The cracked, discoloured mouths and the white eyes create visceral terror as they still remain in human form.
They manage to erode their way through Bowie Base 1, the first base on the planet of Mars, and emerge through faulty water filters.
It must be said, that this is when we see the cockiness of the Doctor, the Time Lord Victorious, and how Adelaide Brooke vehemently disagrees with the amount of power he hold; ultimately taking her own life to ensure that the timeline stays the same, but dying on Earth instead of Mars.
The Flood is also quite similar to the creature of the same name from the Halo franchise.