Re: just ice in the vase
just crushed ice will work. the only thing that the water really does anyway is cool the smoke, there really isn't as much "filtration" going on as everyone thinks...
the only thing that will be hard with only ice is getting the stem to fit all the way in, if you have a mya or another hookah where you can unscrew the downstem i would recommend that, so you can fill up the entire vase with ice.
try it out and let us know how it goes, good luck!