This value is added to the LOD Count of each Water Mesh Component. Negative values will lower the quality(fewer and larger water tiles at the bottom level of the water quadtree), higher values will increase quality (more and smaller water tiles at the bottom level of the water quadtree)
Usage
r.Water.WaterMesh.LODCountBias [value]
Set via the console (~) or in DefaultEngine.ini / DefaultGame.ini.