Minecraft wiki entry for Water, associated text: Water spends most of its time as stationary, rather than 'flowing' – regardless of its level, or whether it contains a current downward or to the side. When specifically triggered by a block update, water changes to 'flowing', updates its level, then changes back to stationary. Water springs are generated as flowing, and oceans, and rivers are generated as stationary. This happens before most types of generated structure are created, and the main cause of water "glitches" is that generated structures do not trigger a block update to let water flow into them.