It turns to ice or heavy water.
it sinks
This item float on the surface of water.
Put it in water and see what happens?
When the water gets warmer the water becomes less dense.
it becomes less dense
Gas is much less dense than liquid.
Cold air is more dense than warm air
Water is more dense.
In the Mediterranean Sea the cool dense water sinks under less dense water which is called density current.
liquid water followed by ice, finally followed by vapor. You can verify this by thinking about what happens when ice is in a cup of liquid water.
Anything that sinks in water is more dense than water.
more dense