Wouldn't thad trip the RCCB in any modern building?
Since the drain is grounded the breaker would kick in immediately.
If the bath was ungrounded, no.
Okay, lets make things more interesting
My claim is that the 'technology' is fairly safe and not as dangerous as you try to portray (when used properly, of course).
1. there are tons of commercial solutions for consumer and industrial market employing this method. I can send you a picture of an industrial heater rated for 25kW used to either heat utility water or provide heating to HVAC systems (NB! directly coupled via conductive liquid to metal fixtures like radiators or kitchen taps). If you want, I can sell it to you for €300 + shipping, it's perfectly functional.
2. falling water does not conduct due to formation of droplets (shower case). Else, everybody who walks out during thunderstorm would already be toast meat a'la hotdogger.
3. water is fairly poor conductor so the resistor network it forms in between the electrodes, human body and the grounding point (fault current) wont normally pass current or potential to matter (e.g. even to trip the RCCD fault current condition).
Obviously, using intrinsically unsafe device (i.e. broken or some hacked/smacked device) will be just as dangerous as with any other home appliance. So if you are stupid enough to heat water in your mouth with this method using two spoons in your mouth connected to mains, then you deserve to die and relieve us from further contamination in gene pool.
Hopefully this stirs things up a bit