However, it is the dynamical correlations which reveal the dierence between the similarities in dierent micro-states (snapshots) and the strong dierences on how the system evolves in time from one microstate to another. Our analysis shows that it is this dynamical evolution which explains several features observed previously in the literature, such as the jump rotation of the OH arm for water , or the contradictory pictures of the importance of the wa-ter structure . Perhaps the water tetrahedrality has been put too much at the center of water local structure ,