Ice is the solid form of water, formed when water is cooled to its freezing point of 0°C (32°F). It's a crystalline structure composed of water molecules held together by hydrogen bonds. Unlike most substances, ice is less dense than liquid water, which is why it floats. This unique property is crucial for aquatic life, as it allows bodies of water to freeze from the top down, providing insulation and a habitat for organisms during cold weather. Ice plays a significant role in Earth's climate, reflecting sunlight and influencing global temperatures.