  The problem of a physical relevance (meaning) of percolation in supercritical
fluids is addressed considering a primitive model of water. Two different
criteria, physical and configurational, are used for the cluster definition in
Monte Carlo simulations over a range of pressures to determine the percolation
line and skewness, and a theoretical analytic equation of state is used to
evaluate response functions. It is found that both criteria yield practically
the same percolation line. However, unlike the findings for simple fluids, the
loci of the response function extrema exhibit density/pressure dependence quite
different from that of the percolation line. The only potential coincidence
between the loci of the extrema of a thermodynamic property and a detectable
structural change is found for the coefficient of isothermal compressibility
and Voronoi neighbors distribution skewness maximum.
