Water is one of two current types of liquid in Minecraft (the other being lava.) It is generally found at layer 64 of the map in large bodies of water, although it is known to be found much higher and much lower. It is impossible to harvest water by normal means, instead, players must use a bucket to pick up the water.
The current physics associated with water only allow for it to flow 8 blocks in any direction. However, it is currently possible to create an "infinite water source" by getting two water source blocks, (the water from a bucket,) and digging a 2x2 hole in the ground. You will then place a single source block in two opposite corners of the hole, and because of the water physics, the water will regenerate every time water is removed from the hole, leaving an infinite water spring.
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