Water arrows are designed much like Broadhead Arrows, the staple arrow type in the Thief
universe, with one key modification: The arrow head has been replaced with a hollow crystal arrow head filled with water. This arrow head is aerodynamically similar to a typical arrow head, but is designed so as to shatter on impact, distributing water to the immediate area surrounding the point of impact.
Water Arrows are one of, if not the most, important tools available to Garrett
; allowing him to perform a number of tasks that range from essential to useless.
- Extinguishing fire-based light sources: Any and all open flames that provide light and are within range of Garrett's bow can be extinguished by a well aimed Water Arrow.
- Dealing damage to fire-based enemies: Water arrows, while typically dealing no damage to humans and creatures, can deal a large amount of damage to fire-based enemies such as Fire Elementals and Fire Shadows, taking them out in one arrow and 2-3 arrows, respectively.
- Disabling Mechanist Robots: In Thief II: The Metal Age, Garrett can disable various steam-powered mechanic enemies by shooting 1-2 water arrows into exposed broilers via the small hole in the unit's back. This technique works on Worker Bots, Combat Bots, and Spider Bots.
- Holy Water Arrows: When a Holy Water Vial is used by the player, all water arrows in the players inventory become Holy Water Arrows for 30 seconds, allowing for high levels of damage against undead opponents