  Anomalous behaviour of the excess entropy ($S_e$) and the associated scaling
relationship with diffusivity are compared in liquids with very different
underlying interactions but similar water-like anomalies: water (SPC/E and
TIP3P models), tetrahedral ionic melts (SiO$_2$ and BeF$_2$) and a fluid with
core-softened, two-scale ramp (2SRP) interactions. We demonstrate the presence
of an excess entropy anomaly in the two water models. Using length and energy
scales appropriate for onset of anomalous behaviour, the density range of the
excess entropy anomaly is shown to be much narrower in water than in ionic
melts or the 2SRP fluid. While the reduced diffusivities ($D^*$) conform to the
excess entropy scaling relation, $D^* =A\exp (\alpha S_e)$ for all the systems
(Y. Rosenfeld, Phys. Rev. A {\bf 1977}, {\it 15}, 2545), the exponential
scaling parameter, $\alpha$, shows a small isochore-dependence in the case of
water. Replacing $S_e$ by pair correlation-based approximants accentuates the
isochore-dependence of the diffusivity scaling. Isochores with similar
diffusivity scaling parameters are shown to have the temperature dependence of
the corresponding entropic contribution. The relationship between diffusivity,
excess entropy and pair correlation approximants to the excess entropy are very
similar in all the tetrahedral liquids.
