Empty Bucket

An empty bucket lifts one tile of liquid out of the world and becomes the filled version. Using the filled one puts that tile back wherever the cursor is pointing. That is the whole mechanic, and it is the only deliberate way to move water, lava or honey around until you find the permanent versions. Shimmer refuses to be scooped by any of them.

The pickup is more forgiving than it looks. Using one checks the three by three area around the target tile for more of the same liquid, and if there is at least half a tile in range, the bucket comes away completely full. That holds even when it removed less than a full tile from the world.

That rounding is exploitable, and it is the standard way to build a lava moat or flood a mushroom farm without hauling anything across the map. Place a tile somewhere it will spread so it splits into fractions, then collect one of the fractions. You get a full bucket back and the rest is still sitting where it flowed. Repeat and the total amount of liquid in the world grows.

Do this with exactly one bucket in your inventory. A single bucket flips between empty and full in the same slot, so you can keep clicking without touching anything else. With a stack you have to reselect the correct slot after every action, which turns a fast loop into a chore. Park the spares in a chest and fill them all when you are done.

Throw an empty bucket on the ground while it is raining, somewhere with no background wall behind it, and it fills with water on its own after a while. Rain clouds and magic droppers do not count. It has to be actual weather under open sky, which makes this a surface trick rather than something you can rig up indoors.

An empty bucket can be worn on your head for a point of defense. It is a joke that happens to work, though a wood helmet does the same job for less trouble and is available far earlier. The genuinely interesting part is cosmetic: put one in the vanity slot and another in the armor slot and they stack visually on top of each other, which almost nothing else in the game does.

A filled bucket is an emergency brake. Dump water or honey underneath yourself on the way down and you land in liquid instead of on stone. Placing it accurately at falling speed takes practice, and Water Walking Boots or an upgrade make getting out afterwards painless.

Lava works the same way if you are already protected, with an Obsidian Skin Potion or a Lava Charm running. The margin for error there is obviously worse, so it is a last resort rather than a plan.

The bottomless buckets place their liquid forever and the absorbant sponges remove it forever, one liquid type each. Both work slightly faster than the hand versions, and the difference shows up most when you drag the cursor around while filling or draining a large area.

Once you own the pair for a given liquid, the plain bucket stops being a tool and becomes a crafting ingredient. It still turns up in furniture recipes and in the Shimmer conversions between filled bucket types, so do not throw the stack away.