The Flood (The Waters of Mars)

The Flood were a viral species which became trapped inside a glacier on their planet of Mars. The Flood needed a physical form to take on and could infect all biological life containing water.

Characteristics
The Flood's natural state was in liquid water. It was capable of controlling the water, causing it to flow in unnatural directions. It was also capable of infecting other life forms by coming into contact with them, making them spasm and convulse as they were taken over, mainly because it was a viral life-form.

Once infected, the individual constantly exuded water, pouring from the body; hands and mouth. This could be increased to produce high-pressure sprays from both the hands and the mouth. The infected victims would no longer draw their oxygen from air, but from water and they would be near walking corpses, as the infection greatly weakened their heartbeats and pulse. Also, the infection would cause a lot of electrical activity in the host's brain. Upon mutation, infected victims could deactivate nearby cameras. When infected, the hosts would also develop cracked skin (especially around the mouth and neck) and blackened teeth, as well as an internal fission in the host's body that produced the water. Some hosts, though not all, could develop faded blue eyes. The Tenth Doctor suggested that this might mean they were closer to human than those with the faded blue eyes. These physical symptoms could be masked, meaning that the infection could hide inside a human host, and infect him or her at any moment.

The host also had the ability to survive on the surface of Mars. Hosts could also run extremely fast, even going as far as to keep up with a rocket-powered robot and outrun other running people. A single droplet of the viral water emitted by the host could pass on the infection to another host. Despite the considerable amount of water produced by the infection, the infected did not seem to be overly affected by electricity (which salty water conducts well); the infected Andy Stone was electrocuted by the Tenth Doctor, but was only momentarily incapacitated. However, the Flood creatures, being made almost entirely up of water and constantly producing it, could be destroyed by intensive heat. This weakness was shared with those who imprisoned them, the Ice Warriors. (DW: The Waters of Mars)

Human victims could no longer speak English, but could emit gurgling growls and snarls and could seemingly only understand Ancient North Martian. All infected could also emit terrifying high-pitched screams that sounded like tortured metal, capable of cracking open ice, and communicating with other infected victims. Strangely, a victim's scream could be heard through the thickest of metals. (DW: The Waters of Mars)

History
On 21 November 2059, the Flood, thanks to a broken filter, managed to infect Andy Stone when he ate a carrot he had washed with water from the glacier. The Flood proceeded to overrun Bowie Base One which eventually led to Captain Adelaide Brooke initiating Action Five. The resulting nuclear detonation destroyed Bowie Base One, the surviving crew, the infected personnel and the Flood. (DW: The Waters of Mars)

In 3289 The Flood began taking over the inhabitants of Erstden after they had infected the water. The Flood possessed members of the Gaian empire and the Gaian resistance group. The Flood were all killed when the Doctor activated the Doomsday Cannon, destroying the planet. (DW: The Doomsday Cannon)

List of Appearances
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Season 49 (2014-2015)

 * The Waters of Mars

Season 53 (2019)

 * The Doomsday Cannon
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