Inspired by Lethal Company, this mod applies an underwater filter for players that are effectively, underwater. No more crystal clear conversations while drowning!

Features

Voices become muffled the moment a player's head goes under the surface.
Real-time amplitude modulation + a bubbling sound effect whenever a player speaks while submerged (the same one from Lethal Company).
Voice range distance is cut in half when you're underwater
Every parameter is configurable!

Voice Chat Hydroacoustics is fully synchronized for all players in the server. You can tune each parameter of the underwater filter in real-time, and every player's client will update instantly.

Commands

/hydro mufflingStrength <0.001 - 1.0>: Adjusts the strength of the muffling. Lower values make voices sound deeper and more submerged. (by default: 0.02)
/hydro voiceVolume <0.0 - 10.0>: Compensates for the muffling by boosting the speaker's gain. (by default: 3.0)
/hydro garglingEffect <0.0 - 1.0>: Controls the intensity of the choppy bubbling modulation applied to the voice. (by default: 0.5)
/hydro bubblingSound <0.0 - 2.0>: Sets the volume of the bubbling sound effect that plays when people talk underwater. (by default: 0.05)
/hydroacoustics voiceDistance <1 - 100>: Sets the maximum block range players can be heard and hear when they're submerged. (Default: 16.0)
/hydroacoustics defaultValues: Instantly restores all settings to their original defaults.

Possible Future Changes

Extended version support
Make the filter apply to any entity that reproduces a sound underwater (currently only affects players).
Perhaps an underlava filter?