As for the water volumes, that is a shame, is there perhaps a way I convince you to implement a way to detect invisible passable entities (when inside) either block or model, as I am not using this function for water volumes, but physics volumes, trigger zones, ect. I have a video of this working here, hopefully this demonstartes its usefulness:
http://www.youtube.com/watch?v=OVYnrP32gFk (the wireframe cubes you see are passable map blocks with data attached) terrain just wouldn't work for this. Worth a shot, thanks.