For very dilute aqueous electrolytes, the conductivity drops very linearly. From some Ω×m at common solutions, the resistivity climbs to ~10MΩ×m for very carefully deionized water at room temperature. Since pure water conducts little, resistivity is a means to characterise the purity of water, notably in the semiconductor industry.
Pure water can even serve as an insulator for a short time, and then its permittivity of 80 and good breakdown field store much energy in little volume. And now I have an excuse to link to nice pictures:
http://www.sandia.gov/z-machine/(the older design with sparks at the surface)