I almost couldn't answer your question due to a pop up ad that covered the dialog box on the home page. I can't remember the terminology but there's something about water where it's volume increases as it's temperature decreases, (kinda opposite of most things) thereby now weighing less than an equal amount of liquid water it would displace. Am I close? I also heard that if you want water to become ice faster you need to boil it first. The topic of water is definitely one of the most interesting of all.
Because when the water freezes up the water molecules tighten up together and is rigid in shape.but when it is in the form of liquid the molecules are looser from each other.