(3) But they do get some help from nature. All liquids have a boiling point and a freezing point. When water boils at a certain temperature it turns into steam. When it is cooled to a certain temperature it freezes and becomes ice. Water boils at 100 degree Celsius (100 °C) and freezes at 0 °C. When the outside temperature falls below the freezing point of water, lakes and rivers get frozen. However, only the top layer of the lake or river freezes. Underneath the frozen upper layer, the water remains in its liquid form and does not freeze. Also, oxygen is trapped beneath the layer of ice. As a result, fish and other aquatic animals find it possible to live comfortably in the frozen lakes and ponds.