Waterlogging

A water source block may occupy the space of a non-solid block, thus filling its remaining "air space". The non-solid block is then "waterlogged". This situation is created when a water bucket is used on a block like a stair or fence post, thus placing a water source in the normal way, but overlapping it in a manner of speaking. If the non-solid block is destroyed the water source remains.

In the effect may also be created using a debug stick.

Mechanism
In Java Edition, certain blocks have a tag which can be either.

In Bedrock Edition, waterlogging is handled by the game's layers system. Through editing, any block can be waterlogged, as well as other things such as placing multiple slabs into a single block.

Behavior
Section may be incomplete.

See report for more info.