Water can update instantly making flowing water very far away from the source block gain or lose the water instantly.

This may be WAI or Won't Fix as this may require changing water code entirely.

How to reproduce

1. Create the Instant Water Setup.png(Place an empty bucket in the dispenser)
2. Break the birch sign

Actual behavior

Two blocks at the edge of the water will flash between flowing water and air, blocks broken below these will do the same.

Expected behavior

The water should not disappear and reappear instantly, and will remain instead of disappearing every time the source block is removed.

Video

See this video by pr0cess for more information and an explanation of this issue.

Note

This is not just a visual issue. You can only swim/interact with the water where it is visible.