The bug
Caves (and mineshafts) are not always properly flooded. Instead the water just stops at some point in midair.
Note: Updating the block is always problematic and only updates one block of water instead of all!
How to reproduce
New example (1.14.3+):
|Seed|6531545027671287273|
|World type|Default|
|Coordinates|/tp @s 170.45 58.00 -634.49 151.94 -50.55|
Old example: Seed:
780093002305051133
Related issues
is duplicated by
relates to
Attachments
Comments


Confirmed.

Worldgen can be crazy.
I would just like to point out that this can also happen with lava.
[unrelated screenshot about MC-125106 removed]
Current snapshot 18w10a, seed 7719836812195502587 and I just teleported to a Stronghold to take a look around. -1545 35 -203 a water fountain isn't "fountaining". If generated "fountains" are not "fountaining", this could be a noticeable issue. Another fortress in the same world, same fountain, same issue.
See MC-125106.

Confirmed in 1.16.1 and 20w27a using the seed and coordinates from MC-153210:
Seed: 4357639008311401092
/teleport @s 245 17 37 -43 -69

In 20w29a.

Can confirm in 20w51a, using the seed and coordinates provided by
@unknown
Happens in snapshot 21w10a as well.
I saw this happen with the new Lush Cave water pools in 20w10a I believe, unless it's a new bug
But if it isn't then this bug really should be more important to fix shouldn't it?
The issue with the old seed (780093002305051133) doesn't happen anymore because generation changed.
The issue with the seed 6531545027671287273 is a larger version of MC-132285. It is caused by caves intersecting with the swamp surface builder that places puddles.
The Lush Caves issue was fixed in an earlier snapshot.
The issue with the seed 4357639008311401092 is caused by intersecting caves and water caves, which is also reported in MC-223227. I suggest keeping it there, as it is a very specific problem.
I recommend only confirming this problem here if it doesn't match one of the issues above, to avoid duplicates. The original issue might already be fixed.

Also occurs with strongholds, especially when the stronghold generates below y=10.

Also note that this happens independently of chunk borders.