The lowest level of flowing water doesn't move mobs

. Can confirm. Quite annoying for most mob farms.

Not only the lowest level, but the 4 lowest levels won't push mobs, if there's a block above their head. See attached screenshot.

Edit: it seems to be affected by how tall the mob is. In this case the creepers are shorter than skeletons or zombies. The latter will travel to the last block, but very slowly.

Most mobs will float above the stream, and stop being transported when they no longer touch it. Zombies and skeletons sink into the stream and get transported further, sometimes even to the end of it.

Affects all living entities and the speed of being pushed seems to be dependent on the immersion, like a creeper that tries to float up in the 2 high tunnel gets stuck in the middle of the stream right around water level 4.

But why 5 days before scheduled release? Eh...

Making the lower water sources slower is a bad idea in general. Flowing water pushing mobs and players has been a mechanic that has been in the game since forever. Is it really necessary to change it now? This will break nearly every water based mob farm. Not to mention that it also seems buggy.

If you want to make things better and more realistic, have ice under the water effect mobs and players by having them pushed faster.

Although there is only minimal grief with this bug currently, it will break the majority of mob farms and will precipitate a sizable uproar if it survives to the final release. Imagine players opening their worlds in 1.13 to find every mob farm/item transport broken with little to no notice beforehand. I would advise carefully weighing the worth of slightly more realistic fluid mechanics against the numerous headaches and agitation this will create. 

@ Jessica Washer,

"because 1 that breaks alot of things"

What does that break? The speed at which my player moves in a water stream has never been an issue for me (or broken anything I've built). So what am I missing here?

And it's pretty much a given that any time you import an older world into a newer version, something may (and likely will) break. That's the price you pay for continuing older worlds in newer versions. While my unbreakable iron farm has survived all updates since it was built in 1.8 (the bugged 1.13-pre8/9 snapshots excepted), my guardian farm has needed to be repaired several times, and will need it again once 1.13 drops.

You can create a separate folder and profile in the launcher for older versions, to keep them separate from newer versions that might break older worlds, then you can choose which version you want to play each time from the launcher.

As far as this issue is concerned, I'm glad it was actually a bug and not an intended change. The player thing may be as well, but that seems like a different issue that should be reported separately (if it hasn't been already).

@ Early Reflections

"Constant speed had many practical uses"

I thought mobs always slowed a little toward the end of water streams. This issue was that they slowed a lot more, and stopped before the end of the stream.

Anyway... the unbreakable iron farm is once again producing at full speed, so it has survived yet another update and will continue sacrificing the noble village protectors without mercy in 1.13. Thank you , Mojang, for fixing this! 👍

Please move any further discussion to r/mojira.

@Timothy Patrick "The speed at which my player moves in a water stream has never been an issue for me (or broken anything I've built)" That's not a valid statement, just because it does not affect you do not mean that it does not affect other players, This behavior affects many buildings or farms where its neccesesary the player actions (right clicking/left clicking) such as nether wart farms, ice farms, mushroom block farms, leave farms, tree farms, breeding farms (bunny farms, sheep farms etc)

Anyway, If this bug its going to lead into a further discussion on wheter it should be as it has always be or if this its the best time to add that, I suggest that the disccussion should be moved into  reddit in the r/mojira sub reddit

This hasn't been fixed if the water is on top fence gates

@unknown: That would be MC-133923.