Water cut volume
Would cut the water out in the shape of the Negation volume as to allow structures to be under the water level.
Edit: How about a feature where you can combine the water meshes(reducing rendering lag like reflections) but the game still processes each volume as a separate box so there’sno need for a major rework.
Allow setting and reusing of planar reflections for multiple water volumes
Sometimes water volumes are on the same plane or their difference is negligible enough so reusing reflections would make it cheaper. (Also why does the planar reflections also render shadows?)
Skybox reflections on High water settings
Skybox reflections should be relatively cheap and would make water look quite a bit better.