Water ice has been studied for over a century. The various experimental and theoretical investigations/approaches revealed their physicochemical behaviours as well as raised further questions. Order/disorder of molecular orientations, also known as hydrogen order/disorder, is one key factor complicating this molecular crystalline system. In this talk, I will show some of my previous works on partial (dis)ordered systems of ice V/XIII and salt hydrate using neutron diffraction compensated with some other approaches.