Water

Water is a block that is fluid; when placed or generated, it will create 'flowing' water blocks that extend seven blocks in any direction. If the terrain lowers during these seven blocks, the count is reset. Water source blocks can be collected using a Bucket or similar container, after which point the flowing water blocks connected to that source block will dry up.

Water source blocks seperated by one flowing water block will form together into an infinite water source. These are commonly created in a 2x2x1 hole, though other configurations are certainly possible. When a container is used on an infinite water source, the flowing water will refill the source block, allowing you to fill up as many containers as necessary without depleting any source blocks.

When Water and Lava meet, they will generate either Obsidian or Cobblestone, depending on whether the blocks are source or flowing. As flowing Water and Lava do not deplete when forming Cobblestone in this manner, a number of designs for Cobblestone generators exist, utilizing Water and Lava to create an infinite source of Cobblestone.

Water can also be used to prevent the player from taking fall damage. No matter the distance of the fall, falling into a block of water will result in the player taking no damage.

Flowing water will interact with a number of non-solid blocks, such as Torches and Redstone, reverting them to items when the two come into contact. This method can be used to quickly collect seeds from Tall Grass.