This crash seems to happen on my server when my friend and I are exploring in a boat (maybe chunk-gen related?).
crash-report.txt

fabric-carpet-1.16-1.4.0+v200623.jar
windows 10
fabric loader 0.9.0 build 204

well, the crash report suggests its an ancient version:

Minecraft Version: 1.14.4
carpet: Carpet Mod in Fabric 1.0.5

Not sure why that is, I'm definitely on 1.16.1 and that fabric-carpet jar name is copy/pasted from my mods folder. Maybe I had an old version of NotEnoughCrashes or something.
Anyways, I haven't been able to reproduce it since posting this, so I'll close it.