Crawling

Crawling is a mechanic that prevents the player from suffocating when inside small gaps. Crawling covers a pose that occurs when the player is in an area less than 1.5 blocks high.

Entering crawling
A player cannot crawl when there is no risk of suffocation. Crawling is initiated automatically in any situation that would cause the player's head to intersect a block in such a way that the area underneath the block is less than 1.5 blocks. For example:


 * Closing a trapdoor on the player
 * Closing a fence gate when it is at the same altitude as the player's head
 * Using a piston to push a block into the player
 * Exiting swimming mode in a one-block-high space
 * Exiting elytra mode in a one-block-high space
 * Having a tree grow over a player
 * Throwing an Ender Pearl into a one block space
 * Having a shulker box push the player down
 * This normally makes the player sneak instead of crawl, but when it is above a slab or a not-full block, then the player crawls.
 * Getting off a pig with a saddle if it's under a one-block-high space
 * Having a boat land on the player's head

In these circumstances, the player automatically switches to a crawling state. When enough space opens up above the player's head, the player automatically exits this state and begins standing again. When crawling, the player travels at sneaking speed. In the crawling form, the player is reduced to 0.625 blocks tall, or $5/8$ of a block, meaning that they can crawl over blocks 0.375 blocks tall, or $3/8$ blocks tall, the height of a daylight sensor.

Bedrock Edition
$$, exiting swimming into a one-block-high space results in the swimming animation. The physics thereafter behave as if the player is flying in creative (but cannot move up or down, and the player falls to the ground when there aren't blocks below them).