Coral

Corals are non-solid blocks that come in five variants: tube, brain, bubble, fire, and horn.

Dead corals are the dead variants of coral.

Natural generation
Corals naturally generate in coral reef structures found in warm ocean biomes.

Bone meal
When using bone meal on dirt, coarse dirt, sand, red sand or gravel underwater, coral will generate in place of some of the seagrass. However, this only works in warm ocean biomes.

Dead coral is created when coral is placed out of water.

Obtaining
Corals can be mined instantly, but can only be obtained when mined with a Silk Touch enchanted tool.

Usage
Corals can be used as a building or decoration block. If it's not placed underwater, it will quickly transform into dead coral. If at any time the block above a coral is removed (such as by using a bucket to remove a water source block or by breaking a solid or transparent block) and not immediately replaced with water (which can flow into the block or be left behind when a waterlogged block is broken), the coral will break and drop nothing.

Dead coral
In order for coral to stay alive, at least one of the blocks surrounding it must be water. If placed outside of water, it will die and transform into its respective dead coral after a few seconds.

ID
Java Edition:

Bedrock Edition:

Block data
In Bedrock Edition, corals have the following block data:

Trivia

 * In real life, corals are colonies of sessile (immobile) animals.