The Most Extraordinary Ordinary

Water. A thing we see everyday in our life. Ice. Another thing we see everyday... well almost everyday. But have you ever thought about how strange ice are water are? I mean ice is the only thing that floats in its solid form. Like butter sinks in melted butter and like copper would sink in liquid copper. Ice, it floats! I know it has something to do with water's structure, but i just don't understand it. I mean when water becomes ice, the density changes from about one to 0.92. I think it has something to do with the water expanding when it freezes, but I'm not sure. Any thoughts?