Water Arrows
From The DarkMod Wiki
Water arrows can be used to put out open flames. For best results, aim slightly higher than the flame you wish to extinguish.
Water arrows can also wash away blood and extend the reach of moss, by shooting an arrow into the blood/moss.
They can also stimulate extra growth in a vine created by a vine arrow.
When you use a Holy Water inventory object, your water arrows become capable of damaging undead for a limited amount of time.