Conversation so far:
How does water freeze?
Freezing happens when the molecules of a liquid get so cold that they slow down enough to hook onto each other, forming a solid crystal.
How happens to waters molecules when it freezes?
When frozen, water molecules take a more defined shape and arrange themselves in six-sided crystalline structures. The crystalline arrangement is less dense than that of the molecules in liquid form which makes the ice less dense than the liquid water.
Why isn't the bottom of the ocean frozen?
Once frozen, the ice insulates the water at the bottom from cooling so its temperature is maintained between 0 and almost 4°C, keeping it from freezing.

Question: Can the bottom of the ocean freeze?
Self-contained rewrite: Can the bottom of the ocean freeze?