This release fixes an issue in new world creation where water creatures were not spawning naturally because the FLAT type of world height of the world became -63, i.e., one block above -64. Unfortunately, this fix doesn't change existing worlds. It can only affect new worlds.
To fix current worlds
Use are your own risk! Take a backup copy of your world beforehand
You need to edit or replace the level.dat file in the bskyblock_world folder. The simple approach is to copy a level.dat file from a generic world and paste over it, e.g. the world folder's copy. Then restart the server, and it should work. Alternatively, if you have a NBT editor, then you can change the level.dat file of the world NBT tags to look like this:

Compatibility
✔️ BentoBox API 2.7.1 or later only
✔️ Minecraft 1.21.3+ only
✔️ Java 21
Upgrading
- Make sure you are upgrading to MC 1.21.3 or later!
- Stop the server. Make a backup just in case.
- Copy this jar over the old one
- Restart the server
- You should be good to go!
Changelog
Legend
- 🔡 locale files may need to be regenerated or updated.
- ⚙️ config options have been removed, renamed or added.
- 🔺 special attention needed.
What's Changed
- Fix for BentoBoxWorld/BentoBox#2593 by @tastybento in #537
- Fixing a possible bug that can interfere with mob spawns in bskyblock generated worlds by @gochi9 in #541
- Release 1.19.1 by @tastybento in #544
New Contributors
Full Changelog: 1.90.0...1.19.1