Squid

Squid are 8-armed mobs that spawn in water. Squid are always passive towards the player, akin to the other passive mobs found on land. They can be found in water from levels greater than 45 and lower than 63, and they can spawn in any biome or difficulty.

Appearance
Squid have 8 tentacles, blueish-teal skin and teeth that can be found underneath the head. They have two eyes which appear wall-eyed. Despite being called squid in-game, their body arrangement is closer to that of a real-world octopus.

Uses
When killed, each squid will drop 1 - 3 ink sacs, each of which can be used directly as a unit of black dye. Like any other dye, an ink sac can be crafted with or applied to various items to recolor them: wool, leather armour, hardened clay, a sheep, or a dog's collar.

An ink sac in particular can also be crafted with varying proportions of bone meal to yield light gray and dark gray dyes, or with a feather and a book to produce a book and quill.

Behavior
When moving about, the squid's tentacles open and close, giving them an appearance of pushing themselves forward. Squid will hover in place and wander around one layer aimlessly, are not attracted to light and do not deliberately interact with the player. However, if attacked, squid will attempt to swim away from the player.

Squid could stay alive but become immobile when beached on the land until before 1.4.4pre. From that version they suffocate in air or if in water that is too shallow for their liking, meaning you can find natural ink at the edges of ponds. They can take fall damage and burn like any land mob, but, due to being aquatic they cannot drown.

Squid cannot swim in lava, even if given a Fire Resistance potion. They simply pass through the lava and behave as if on land.

Squid (unlike land-based mobs) can swim against a current and not get pushed by it.

Farming
Squid, although able to swim against the current, can not swim up a waterfall. The simplest way to automatically farm them is to place a 3x3 platform of hoppers two blocks beneath the floor of a reasonably-sized water source (river, lake, swimming pool...), preferably in your spawn chunks. Ensure these hoppers all lead to one of the hoppers. Optional: A chest can be placed for the output of the final hopper if more than a dozen stacks of ink are required! Place columns of 4 signs above each hopper, then destroy the layer of signs second from the top. Squid will be sucked down by the falling water, into the waterless 2 high signage, suffocate and their ink collected by the hoppers. Optional: Dig a dry tunnel under the water source from the banks to the output for ease of collection.

For larger farms, dig an approximately 8x8 hole three blocks deep at the bottom of an ocean or large lake. The fall of water into the hole will trap squid that wander over it. Complicated funnel and channel systems can bring squid from multiple traps to a central location for the player to kill.

Trivia

 * Hitting a squid underwater causes them to rise approximately 1/3 to 1/2 a block.
 * Squid cannot be damaged by attacking their tentacles.
 * When out of water, Squids are extremely resistant to knockback.
 * Squid behave like some land mobs and attempt to ride a Minecart, however this is not always useful as rails and water cannot occupy the same block.
 * Squid are the first passive mob that spawn at any light level, in water, and without grass.
 * When the world is loaded, all squids are aligned with the tentacles facing east.
 * Squids are one of the few silent mobs in Minecraft, along with Witches and Snow Golems.
 * In RC2, when Squid came out of the water and were hurt, they made the new player hurt sounds.
 * Squid and Bats are the only passive animals that cannot breed; due to this, however, they will spawn randomly (similar to hostile mobs).
 * It is possible for a squid to receive fall damage.
 * Squid, along with Ocelots and Bats are the only passive mobs that can despawn.
 * It is possible for squid to spawn in the fountains of Strongholds, underground lakes, wells, obsidian patches, cobblestone generators, and caves with water running through it.