from an Electrical Engineer's point of view...
GROUND does not mean "the ground", but merely refers to a return path for the electricity.
Rubber blocks the individuals from "the ground", but not from the return line (the neutral wire) and the earth ground wire.
Therefore, the electricity wants to go from the "hot" wire to the "neutral" wire (or earth ground), and the only way it can do that is through the water.
That being said, it can be assumed that most of the charge will go straight from the hot to the neutral, but some of the charge will take the long way through the surrounding water (and those retarded German individuals).
(My $24,000/year education has now paid itself off.)