Suffocation

Suffocation is when a player or a mob is unable to breathe due to his upper half being inside of a block. They will lose half a heart every 0.5 seconds. Due to sand and gravel falling, it can easily cover the player. In first person mode, the player's screen will be blackened when suffering from this condition thus disabling them to see what is happening. In third person mode, the player can clearly be seen being inside the blocks.

When inside a block, the player can easily step out of it as the blocks do not block their movement.

Causes
The usual ways to get one's head inside a block are:


 * Sand or Gravel falling into the space the player or mob occupies.
 * Riding a Boat or Minecart into a one-block-high space.
 * Riding a pig into a two- or one-block-high space.
 * Standing where a tree just grew from a sapling.
 * If you save near bedrock, and then reload, its possible that you spawn inside the bedrock, killing you since you can't move or dig the bedrock out.

History
In Indev before suffocation was implemented, players that were covered by blocks could see through dirt and stone. Suffocation was added after Notch discovered that players were abusing this exploit to find underground caves and hollowed carvings. The patch added suffocation damage and making the player unable to see anything when experiencing it. However, this glitch is not completely fixed and is still possible to be done even in the existing version of the game.

Patches

 * After the July 9th update, players no longer suffocate when riding in a minecart.
 * After the November 10th update (version 1.2.2) players no longer suffocate when they get out of the minecart while inside a two-block-high tunnel. The same applies when disembarking a boat.

Glitches
Although the screen is blackened in first person mode, players can still see through gravel or sand blocks to locate caves using third person by adjusting the camera angle correctly.

Now The Void can be seen and caverns can be easily located. It is more beneficial to do this during the day because The Void will emit light and caves will be more visible against it. This glitch is best performed on Peaceful Difficulty so that the health that you lose from the suffocation can be regained.

This video demonstrates a player suffocating. By changing the view into the third person it is possible to see through the blocks.

It is also possible to use this glitch without getting suffocation damage in first person mode, however. This is done by, backing out of the blocks just enough that the character is still technically in the blocks but not enough to be suffocating. Then move slowly toward the blocks until the near clipping plane of the view is inside the gravel or sand. Sneaking works rather well here.

Trivia/Bugs

 * Steps will not cause suffocation. As a result, placing a step above a minecart track can be used to make a barrier through which carts can be ridden without allowing mobs (other than 1 block high chickens) to wander in.