i never had this problem with grass !
and to be honest, i never had the time to check the MJV solution but Martin was pretty positive about the result.
and yes the water is a disc (with a "max radius" setting), and i always use it because usually i create a scene, shaders, atmo, and then i hunt down my pov.... and sometimes, the definitive pov is faaaar away from the point i created the all scene