How come water exists in all 3 states in its triple point?
Most of water's interesting physical characteristics can be traced to the nature of the hydrogen bonds that comprise it.  We tend to think of water as H2O a unitary molecule.  The reality is that the hydrogen bond is somewhat weak and you really have is more of a soup. \n\nThis behavior of water is so unique that people have mad careers of studying it.  Indeed it is said by some that if water did not exhibit the characteristics that it does life itself could not exist.
How very astute.  Fluids form mixtures and circulate based on different things, like pressure and heat.\n\nBut the gases do form layers.  Who said they don't?