Bubble Column

A bubble column is a fluid generated by placing magma blocks or soul sand in water (source). Bubble columns push or pull entities and items in certain directions.

Breaking
Bubble columns cannot be obtained as an item, and can be placed only by a block-placement command such as.

$$, it may be obtained as an item via inventory editing, add-ons, or bugs.

Natural generation
When generating the world, caves, aquifers and underwater ruins generate below the water surface. All bubble columns generate bubble column blocks until the column reaches the surface of the water or a solid block above the magma block.

Post-generation
When a magma block is placed underwater, a whirlpool bubble column is generated.

When soul sand is placed under source water blocks, an upward bubble column is generated.

Usage
Players and other air-breathing mobs can enter a bubble column to replenish their air supply, at the same speed that they would when they leave the water entirely. Water-breathing mobs avoid bubble columns because they suffocate if trapped in one. A bubble column is destroyed when moved by a piston. Bubble columns propagate only through water source blocks, stopping at any flowing water or waterlogged block. The height of a bubble column is limited only by the water's surface or by any obstructing blocks underwater.

Bubble columns cannot be created in downward flowing water. Placing a kelp plant in downward-flowing water converts it into a source block.

Whirlpool
A whirlpool, or downward bubble column, is the most common type that generates in the Overworld, often originating from magma at the bottom of underwater canyons. A whirlpool can be identified by the presence of air bubbles wandering downward. They drag entities downward. A boat ridden over a whirlpool shakes and eventually sinks if kept above the whirlpool for too long.

Upward
Upward bubble columns can be identified by the presence of vertically rising air bubbles. An upward bubble column accelerates entities upward. The longer an object rises through the bubble column, the faster it travels. At high enough speeds, players and entities can be launched out of water by several blocks. Sitting on the surface above a rising bubble column causes entities to bounce upward repeatedly by about 1 block.

Transport
Entities move at a speed of approximately 11 blocks (meters) per second when ascending a bubble column or 4.9 blocks per second when descending a bubble column.

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