Morgans wrote:

Water has the unusual property of getting less dense, when it gets
to almost
freezing. That is the only thing that keeps lakes from freezing solid, from
the bottom up. Most things get more dense as they get colder, so the cold
sinks to the bottom of the container, but not water.

No, that isn't the only thing. The ground stays warmer than the air
during the winter, so water would still freeze from the top down even if
the density didn't change during the phase change.


Matt