These videos were recorded with a Canon Powershot S50 digital camera. They have not be altered in any way, other than to reencode them to xvid from mjpeg to reduce size. I assure you that the liquid you see in them is truly water with nothing added to it. It is straight from the bottle. The bottled water I happened to have was Nestle Pure Life Purified Water.
Some quick googling reveals that supercooling is a well-documented, though mysterious, behavior of water. What it means is that water, if it contains relatively few impurities, can be cooled to below its freezing point without crystallizing. But if you disturb the water, it instantly crystallizes. I'm tempted to try this experiment, but with the temperature outside in the 60s here in San Diego, I'll have to use my freezer.