Simplified phase diagram of water, and thermodynamical properties inside a 5 M_⊕ planet, containing 0.5 M_⊕ of water, with surface temperature equal to 370 K and surface pressure at the vapour/liquid transition. The Fe/Si and Mg/Si ratio are equal to the solar values. The temperature and pressure are plotted in brown for the silicate/iron phase, and in blue for the water. As can be seen on the figure, this planet presents a large layer of high pressure ice, preventing habitability.