I would do this with some creative EQ filtering on the primary audio track (mid-low pass randomized filters) and overlaying some water-like sounds. (I would stick a microphone underwater for those sounds.)

In theory-crafting, convolvers are primarily used for reverb, but I am wondering if a water sound track could be used instead of a typical impulse recording… Dunno. I have the tools for all of that, so it would be interesting for me to try that tonight, actually. (I am new to convolvers, so it may not be possible at all.)

Yes it can, I’m not sure what the process is called or how it’s typically done but I can accomplish this by playing with the EQ settings when editing videos in Davinci Resolve.

You need an envelope follower to trigger or to modulate something in track 2, according the waveform of track 1

Read this

Comment #2. So I played around a bit and got something muffled and a bit wobbly. It was basically mix of cropping out highs/mid-highs and adding various depth effects, mild hiss and some compression with actual water sounds that are playing super quiet. After all that mess, I EQ that again to get rid of any clipping or popping.

It’s still not perfect but might be on the right track. I am in a road trip at the moment but I just randomized a piano and started slapping fx together. The fx are completely blown out on my phone speakers, but decent enough with headphones.

https://filebin.net/kdqlljwwwoknaeg5/water_sim.mp3

Here is what I am working with so far. You can see the fx chain in the right side. EQ -> Luxverb for depth -> Basic delay and reverb -> EQ #2 -> flange for a bit of hiss. (Track 5 hits the limiter on Track 1 for a bit of water-like wobble.) The first EQ low pass is purposely high. It creates a bit of distortion that kinda works.

We need a community for these types of questions I think. You probably want to put a low pass filter on and work from there.

Edit: !musicproduction@sh.itjust.works seems appropriate