Water is one of the few substances that expands at reduced temperatures, so density decreases and ice floats. I'm not a chemist, but I guess it must be the molecular structure - a big atom with two little ones attached, also the best solvent around - that makes it grow, not shrink, when it cools down.
Hmm... funny things about beer, without being a jackass... I was at the store, picked up a case of Guinness. The handle on the box ripped and the box fell out of my hand, a couple bottles broke and the precious liquid began to spread on the floor around the box.
I told the cashier what happened, and said 'I hate when I break beer!' and she said, 'Yeah, it is such a waste'. She didn't really look like a 'beer drinker', but I could tell she understood.