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Nightmare Fuel: Survival of the Dead
Zombies residing at the bottom of a lake, clawing at any human that dares swim by, is pretty damn scary, especially if you can't swim. Fridge Horrorsinks in if you think about how this could apply to any body of water that had people around it at the time of the Zombie Apocalypse, and is deep enough for them to stay in.
Also, "alive" zombie heads on pikes, still moaning.