Take a look this this: https://imgur.com/a/w8gOxxP
As the camera moves further from the fluid and the viewing angles gets lower, the more this dark reflection appears in the liquid's surface. I removed all reflection probes from the scene to see if that had something to do with it, to no effect. Looks like a screen space reflection, but it's way too dark for the fluid and environment. I'm using the default fluid renderer with nothing changed other than the surface downsampling seen in the pictures, but I also reverted that to see if it would make a difference.
Update:
This only affects VR rendering. Here's a comparison between the exact same scene from the exact same perspective with nothing changed other than the render target: https://imgur.com/a/2Gzumv8
As the camera moves further from the fluid and the viewing angles gets lower, the more this dark reflection appears in the liquid's surface. I removed all reflection probes from the scene to see if that had something to do with it, to no effect. Looks like a screen space reflection, but it's way too dark for the fluid and environment. I'm using the default fluid renderer with nothing changed other than the surface downsampling seen in the pictures, but I also reverted that to see if it would make a difference.
Update:
This only affects VR rendering. Here's a comparison between the exact same scene from the exact same perspective with nothing changed other than the render target: https://imgur.com/a/2Gzumv8