The bug
When not aggravated, blazes will sink to the bottom of water or lava instead of floating at the surface like most non-undead mobs. They are still able to fly upwards if hostile.
To reproduce
Spawn a blaze in water or lava while in Creative mode.
Code analysis
This appears to be because blazes don't add a FloatGoal
in net.minecraft.world.entity.monster.Blaze.registerGoals()
, unlike most non-undead mobs.
Linked issues
is duplicated by
Attachments
Comments

Confirmed.
same applies to water. Blazes in the new snapshots will kill themselves in water because they don't try to get out of it.

This ticket has been marked as a duplicate of MC-49937, in favor of the more general or better information provided.

Reopening this ticket and separating from MC-49937 because the issue is still existing.
Copying over this info since it seems useful:
Blazes used to float in water and lava in 1.7.10 and 14w05b, and no longer do in 1.8 as of 14w06b.
For reference, 14w06a is when all mobs got the new AI.
Still confirmed in 1.8-pre3 with screenshot attached.

still present in 1.8 release
confirmed for 1.8
Is there a fix planed for 1.8.1?
If it was fixed for 1.8.1, this would've been resolved already.
Thats why i wrote "Planed". There is no Date yet for the release, thats why i have still the hope that mojang will fix that annoying bug.
EDIT//
Okay, it seems there will no fix for that. Too bad. But at least the sprint key is now in the right category, what a gamebreaking bug...

Confirmed for 1.8.1-pre1.
Also the title could be changed to Blaze not swimming in water or lava since this happens in water too.
Yup, they used to be able to swim in water in 1.7.
This might have something to do with their new AI, since they started doing social aggro (like zombie pigmen) in 1.8.
This is really annoying, built a double blaze grinder and when im about to test it, i figure out this bug exists...
I can relate.

Confirmed in 1.8.1.
I confirm for 1.8.2 pre6
Maybe useful info: Blazes are slowed down by lava when falling (they do not fall through lava like through air).
Still doesnt work in 1.8.8
This is still an issue in 15w47c.
This is still an issue in 15w50a.
This is still an issue in 15w51b.
Guess what. Still not fixed in 16w05b.
Still not fixed in 1.9. Dual Blaze farm still useless 😞
This is still not fixed in 1.9.4
Still an issue in 1.10.2

Confirmed for 17w13a.

Confirmed in 1.12.2 and 17w45a. This appears to be because the initEntityAI()
method does not call this.tasks.addTask(1, new EntityAISwimming(this));
(unlike most mobs), which removes the "swimming in liquids" behavior.

Confirmed for 18w05a.
Can confirm for 18w14b.
Other mobs affected: bats, phantoms, and ghasts. They don't seem to know that they need to be above water to not die. Zombies don't swim up either, but I think that's related to the Drowned mob not this.
Can confirm for 18w22a.
Non-undead mobs that won't swim up but should:
bats
blazes
Undead mobs that do swim up but shouldn't:
zombie horse (MC-129262)
Can confirm for 18w45a.
Non-undead mobs that won't swim up but should:
Bats
Blazes
Endermites
Ghasts (can't actually tell if they are trying to swim up, or just flying around randomly)
Silverfish will swim to surface, but don't actually surface so they drown anyway. (MC-134755)
Can confirm in 20w48a.
Can confirm in 20w51a.
Can confirm in 21w03a.
Can confirm in 21w05b.
Can confirm in 21w06a.
Can confirm in 21w07a. Video attached.
Can confirm in 21w11a.
Can confirm in 21w14a.
Can confirm in 21w17a.
Can confirm in 1.17.
Can confirm in 1.17.1.
Can confirm in 1.18.1.
Can confirm in 1.18.2 and 22w11a.
Can confirm in 1.19.
Can confirm in 1.19.2.

Can confirm in 1.21.4.
I tested this, it's true...