http://farside.ph.utexas.edu/teachin...es/node44.html
"However, in experiments in which a capacitor is submerged in a
dielectric liquid the force per unit area exerted by one plate on
another is observed to decrease... (...) This apparent paradox can be
explained by taking into account the difference in liquid pressure in
the field filled space between the plates and the field free region
outside the capacitor."

So the pressure difference will constantly pump water through a small
hole punched in one of the plates, won't it?

Pentcho Valev