According to Godot documentation and the developer's twit, VoxelGI is not proper to dynamically generated geometry mesh in runtime (https://docs.godotengine.org/en/latest/classes/class_voxelgi.html, https://twitter.com/reduzio/status/1401589094237540364)

As VoxFlow will generate fluid via CubbyFlow in real time, SDFGI seems more desirable for this project.