The Reservoir is a utility seen in Shangri-La. After opening the door next to the mud maze, the player will see a large rock. If going to the flat end with an extended brick, it will say "Don't hold (interact button)." If the player interacts with the brick, a rush of water will trip and temporarily stun any zombie in the rushing water. This is useful when running away from a horde of zombies. Players will be pressed against the edge, but will not fall. However, it is very hard to move against the current.
- It seems that the trap was going to cost points, but then was changed in the final cut. In the Annihilation trailer, a normal trap-activating switch can be seen on the rock, but it was replaced by the brick when the level was finally released.
- The warning when the player is about to press the button is similar to the warning in "Museum", a bonus level in Call of Duty: Modern Warfare 2.