The answer is "no". Assume that the ground wire has a resistance of 1 ohm, and your step father has a resistance of 100,000 ohms, which is actually a bit lower than the "normal" value when measured with dry hands. This means that your step father will experience a current flow that is 1/100,000 times the current flow through the ground wire, assuming that there is a short circuit in the water heater. In addition, since the ground wire has such a low resistance, there will be a LARGE current flow through it. This current flow will immediately trip the associated circuit breaker, shutting off current to the water heater. Unless your step father happens to be touching the ground wire at EXACTLY the time that the short circuit happens, there will be no current flowing through him. Even if he is unlucky enough to touch the ground wire at the exact wrong time, the current flow through him will be so low, and last for such a short duration, that no harm will occur.