Waterskins are a portable drinking utility. In spite of their name, they can be used to carry any kind of beverage, not just water. To fill one, simply right click on a barrel holding a drink.
Unlike other vessels, these can not be placed on a surface as blocks. Hence, they can only be drunk from by holding them in your hand and holding right-click. Also, you can right-click an empty vessel with a full one in your hand, or vice versa to transport the fluids to and from each other.
Obtaining[]
One way to obtain waterskins is by looting. They are often found in Dorwinion (most often in breweries). They are also frequently found in Gondor structures (mostly taverns) and in Lindon structures (especially in halls).
If you don't like to steal waterskins from buildings, and would rather hunt some animals for their hides, then you can craft your own. Besides string, you need three of either leather, fur, lion fur or gemsbok hide, which can not be mixed. Then use the following pattern on a vanilla crafting table:
