The fourth pre-release for Update Aquatic is now available!

A full changelog for this pre-release can be found on Minecraft.net. 

CHANGES IN 1.13-PRE4

• Updated LWJGL
• Biome names are now sorted alphabetically in the buffet menu
• Performance improvements
• Bugs got fixed!

FIXED BUGS IN 1.13-PRE4

• MC-36030 - Music playing despite music / jukebox slider set to OFF
• MC-121798 - Can only scroll list in superflat preset selection when it is focused
• MC-126162 - Waterlogged blocks and bubble columns don't absorb explosion damage
• MC-126244 - Extreme lag when using the /locate command or when generating explorer maps
• MC-126595 - Blue Wither heads are intangible and invincible on the first tick(s?)
• MC-128299 - Blocky and fully bright areas appearing underwater
• MC-128690 - Water does not flow sideways when there’s no block below it
• MC-130270 - Iron golem spawning inside blocks
• MC-130530 - Water source block gets destroyed from downwards flowing water
• MC-131094 - Projectiles ignore collisions for ~1 block after spawned
• MC-131462 - Coordinate math error causes structure not to generate and possibly other issues
• MC-131768 - Models’ predicates are inverted
• MC-131773 - Comparators from command blocks no longer output results properly
• MC-131805 - Observers pulsing after being moved instantly after triggering
• MC-131825 - Enchanted books lose enchantments when upgrading
• MC-131849 - Duplication bug

To get pre-releases, open your launcher and go to the "launch options" tab. Check the box saying "Enable snapshots" and save. To switch between the snapshot and normal version, you can find a new dropdown menu next to the "Play" button. Back up your world first or run the game on in a different folder (In the "launch options" page).

Please report any and all bugs you find in Minecraft to bugs.mojang.com.

Pre-releases can corrupt your world, please backup and/or run them in a different folder from your main worlds. 

Share your thoughts on how 1.13 is shaping up in the comments below!