The water is full of salts or ions, and so is your body (pure water is a poor conductor, needs ions), so conduction should be possible. Voltage would matter if it was great enough that the parallel current flow through your body was sufficient to meet the threshold of bodily damage.
Resistivity is the amount of resistance with respect to how far you are away from a source. Its units are Ω·m, or ohm-meter, or the amount of ohms per meter of seperation. It's based on the lead/probe surface area, and the distance of the conduction path. How many amps pass for a given voltage when probes are at certain distance apart and have a certain surface area.
ρ = (ΩA)/L
ρ = resistivity
Ω = ohms of resistance
L = proximity of conductors
A = surface area of conductors
When you're in the bathtub with a sunken energized cable, you're effectively creating a cct with yourself as 1 resistor and the bathwater as another resistor, in parallel. Depending on your body EC and the bath water EC (resistivity = 1/EC), a resistance can be calculated for both "resistors," (yourself and the bathwater), and because parallel ccts have the same V across the parallel components, one could see it's not hard to electrocute.
After a quick Google search I found 150mA to be a lethal current flow for humans, so if your cord were 120V..
V = I·Ω
120V ÷ 0.15A = 800Ω
...and the conduction route through your body were 800Ω or less, you're a goner! (Not sure how long 100mA - 200mA needs to flow though)