The Bucket is a common tool which is used to transport liquids, both water and lava, from one location to another. Upon using the Bucket on any body of liquid, that liquid type will occupy the Bucket and can later be poured into a pit.
Picking up liquids with a Bucket will not consume the liquid, and a single space of liquid can be used to fill a Bucket endlessly.
Because the source liquid is not consumed upon filling a Bucket, only one trip to a specific location to obtain a liquid is needed: The player can simply empty the Bucket into a pit and then refill the Bucket from the new liquid source without depleting it.