Scientists modeling the H20 in the extreme conditions inside Neptune have now pushed the substance into a superionic state, as hard as iron and (thermally) glowing yellow. Based on what I could google, a superionic state is not yet hot and compressed enough to be metallic, so the hydrogen atoms have free run, but the oxygen remains in a crystal lattice. The superionic state for water is possible at a chilly 7000 K (about 12000 farenheit).
For an introduction to the technology involved, click here. I've had trouble locating a lattice definition of the state, but I did find this abstract list which suggests that the state may also be present in the earth's mantle, right after Ice-VI (no Vonnegut )