Final answer:
Ice has a lower density than liquid water due to the lattice structure formed by hydrogen bonding, making it float and providing an insulative layer for aquatic life in cold climates.
Step-by-step explanation:
The order in solid water (ice) results in lower density, so ice floats on water; other solid states generally sink in their liquid states because they usually have a higher density. When water freezes, its molecules form a lattice structure due to hydrogen bonding, which spreads them further apart compared to the more compact arrangement in liquid water. This unique property of water is crucial for aquatic life. In cold climates, a layer of ice forms on the top of bodies of water, providing insulation and allowing organisms to survive in the liquid water below throughout the winter.