Hot water freezes faster than cold water

Did you know that hot water freezes faster than cold water?

There are different theories about this fenomenon.
The most common theory is: The proces of freezing starts with tiny air bubbles. In cold water (cold water contains more of these bubbles than hot water) an ice layer is formed at the surface and the edges of the water. This layer has an insulating effect on the water, making it freeze less fast. This ice layer is not formed in hot water, making hot water cool (and freeze) faster.