10 Best One-Time Only Doctor Who Villains
5. The Flood (The Waters Of Mars)
Doctor Who seems to enjoy making ordinary things feel scary. Shadows, statues, gas masks, things in the corner of your eye... and in 2009's The Waters of Mars, water.
Another base-under-siege story, this chilling standalone episode is set within the Bowie Base One on the planet Mars, where the Doctor and several crew members are forced to try and contain a water-based infection called The Flood, which transforms its victims into zombie-like creatures that are constantly emanating water.
The Flood doesn't have a true physical form, and instead, it spreads between various life forms (scarily, just a single drop of water can lead to infection) and alters the appearance of its hosts, like the humans within the base, who develop cracked skin around their mouths and discoloured eyes. The look of these Flood-infected humans is creepy as hell, with the cracked skin proving some of the most brilliant makeup work we've ever seen in the show.
Combine these chilling looks with the Flood's merciless, relentless and almost unstoppable desire to spread - and the fact that deadly water is a simple yet inherently spine-tingling idea - and this rather moist entity is an absolute winner of a bad guy.