/kit water Nuff said. Hopefully we can get a plugin developer to create permissions for ice, sort of like water. Whoever places the ice, can destroy it but nobody else can who doesn't have the special feature. or just nobody in general...
or this http://forums.bukkit.org/threads/misc-freezeice-v1-0-ice-and-snow-will-not-melt-1000.26759/ this will make it possible to sell ice in the server shop
