The game crashes when using this mod with Optifine
log: https://paste.ee/p/gtXfM

Seconded, it's happening with me in current version (1.4.3)

Same, crash if also using optifine with the last version of the mod in 1.18.
Crash report says it's a mixin failure of onApplyFogUnderWater function. This must be a conflict as it occurs only with optifine.
crash-2021-12-17_23.55.49-client.txt

Am not planning to add compatibility with OptiFine in the future--sorry!