Answer:
Hydrogen bonds make water molecules spread out when they freeze. This makes ice less dense than water and allows ice to float. If ice did not float then oceans and lakes would freeze from the bottom up, killing marine life by trapping organisms in the ice. When ice floats, it insulates the water below, keeping it at around 4 degrees C or 40F, which does not freeze and allows fish to survive the winter.
Explanation:
