Minecraft (Pocket Edition)
A Water Bucket is obtained by taking a Bucket, selecting it as your active item, and tapping on a source of water (river, waterfall, underground stream, etc). If it is running water it is important to tap near the source of the water.
Usage / Purpose
Water Buckets are invaluable to have in your Hotbar (inventory at bottom of screen) when mining near Lava. If you accidentally bump into Lava you can immediately douse the area with Water. A Water Bucket is also useful to put out fires that have gotten out of control (forest fires started by Lava or Villages set ablaze by glitchy Furnaces).
A Water Bucket is also essential for transporting water from its source to your Garden, if you've set up homestead away from water.
Each Water Bucket requires one inventory slot.
Once the water has been poured from the bucket you are left with an empty bucket. Empty buckets can be reused endlessly.