Im mentioning this as a fine tuning example perhaps..
Ice Does not sink. Yet, nearly every other material in the universe sinks in it self as it gets colder.
Reason being as it gets colder the molecules come closer together, and it becomes denser per volume sinking in its own liquid. (colder water is at the bottom of the pool)
The Reason is, because even though water does become denser as it gets colder towards freezing, when it does freeze its hydrogen bond together and forms a lattice which has more space in btween it, allowing it to float.
Quite amazing, you would think it would just get denser, Ice is harder than water after all, yet not as dense. Like nearly every other material, even Hydrogen on its own will become a solid and sink in liquid hydrogen.
This does not seem like a big deal, but.... what if ICE sank in water?
It would sink to the bottom of the ocean. What lives at the bottom of the ocean? crustaceans, some of the earliest life forms from the Cambrian period.
We probably would not be alive today if it was not that ICE floated.
So, we now How... So why would ICE do that ? why does Ice float instead of sink?