UnderwaterFX is a FREE open-source underwater filter plugin for Windows

Developer ypichev has released UnderwaterFX, a free and open-source creative multi-effect plugin for Windows.

UnderwaterFX is built with C++ and the JUCE framework. And the idea behind it is pretty cool – it makes your audio sound like it is being heard from underwater.

I am always on the lookout for unique sound design tools, and this one does a great job with a relatively simple concept. It gives you those deep, muffled sounds we’ve heard in dozens of movies during underwater scenes, flashbacks, and similar sequences.

Obviously, I will use this for cinematic sound design projects, but I can also see it working nicely for transitions and drops in electronic music. You can, for example, automate this before a breakdown, then snap back to the dry signal when the beat returns.

Under the hood, UnderwaterFX combines a custom low-pass filter, stereo chorus, and spatial reverb. All of this is controlled by the Main FX control, a macro knob that scales the overall underwater effect.

You can simply turn it up, and the sound gets deeper and more submerged without needing to adjust every processor separately.

I love this one-knob approach for quick automation, and it’s super handy if you want to move from a dry signal into a full underwater wash over a few bars.

However, if you want more control, Manual Mode unlocks the individual sub-effect controls. Dive lowers the filter cutoff, Reso adjusts the resonance, Chorus controls the modulation depth, and Reverb sets the amount of spatial effect.

You can double-click knobs to reset them to default values, and you can click the value display below a slider to type an exact numerical setting.

Now, of course, this won’t be everyone’s cup of tea. UnderwaterFX is more of a focused sound design tool for lo-fi textures, ambient stuff, and cinematic sound design.

The project is open-source, so developers can inspect or modify the code on GitHub. The repository also includes build instructions for anyone who wants to compile the plugin for another system.

UnderwaterFX is available as a 64-bit Windows VST3 plugin and standalone app. There is no pre-built macOS version at the moment, but I would love to see one soon.

Download: UnderwaterFX (FREE)

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Last Updated on June 3, 2026 by Tomislav Zlatic.