Problems with onwater()

[kingcj]

I have a custom bomb that works fine with default pics0 (I guess) graphics. If the bomb is dropped on water it "sinks" using destroy(), and it is checked severside with the onwater() command.
However when the bomb is dropped on a custom tileset using the same onwater command, it doesn't "sink" the bomb. The tiles are water according to clientside putleaps and clientside custom movement system that is being used, but checking with onwater severside won't pick up the water.
Is there a way around this or is this just an odd glitch that I've run across? I don't really know anyway around it. I've tried placing the custom water tiles in a var and check the - tiles[x,y] in var -, but it doesn't seem to work serverside either.
Again, the bomb works perfectly with default graphics, but when placed in custom water tiles, the bomb doesn't "sink."