Describe the bug

You can see here, also it happens without optifine installed

How to reproduce the bug

Go in oil 2 deep blocks

Expected behavior

not be transparent

Additional details

No response

Which Minecraft version are you using?

1.18

Crash log

No response

Duplicate of #861 and others

It's not a duplicate since the original issue was made for 1.16 and was closed with this comment

Modded fluids simply don't behave like water, and won't until at least Minecraft 1.17.
While this one was made for 1.18

I also believe you can add water-like physics to fluids by adding them to the #minecraft:water tag now 😄

The fluid update is in Forge 1.19, and recent 1.19 PNC builds use that for proper fluid physics. There is zero possibility of that ever appearing in any earlier version of the mod.

You can indeed add water-like physics to fluids via tagging, but that could cause unexpected side effects, which I have no intention of supporting...