From what I can see, it’s the so-called “water albedos” that control this. What’s lacking, is documentation how these can be modified (which would be quite useful as many of us agree).
The VFS Projector reveals the following:
VFSProjection\cgl\base\wabworld.cgl
VFSProjection\cgl\base\waterblurmasks.cgl
VFSProjection\cgl\base\waterblurmasksoffline.cgl
VFSProjection\cgl\base\waterclassification.cgl
All of them seem to be global and it is not clear if any of these influence underwater albedos like coral reefs.
Then there are the more detailed CGL files loaded from the cloud like this one, which can be found through tile debugger in DevMode:
https://sunriseworld.akamaized.net/sr-results/water_albedo/2025_01_31/water_albedo/wab032203.cgl?version=0
Files like these most certainly control the display of underwater albedos.
Question now is how we can add these to our packages similarly to the well known sai*.cgl files?
The process for that might be pretty simple and straightforward - if it would just be enabled in the SDK that we can write CGL files with the appropriate header - and MSFS2024 being able to find those.