Perhaps if BAS's links are to much to understand then employing an electrician would be quite a sensible idea, after all, who wants to burn their own house down or hurt / kill someone though arrogance? I am not being b!tchy here, it is an electric item, spraying water onto someone who will be naked and as such, a good conductor at the time, mo so than normally! It is important that this work is done safely, the problem may be what you dont know, not what you think you dont know.
The cable could be 10mm but I doubt it, is the CPC (earth) a multi stranded copper wire or a solid wire??
Can you 100% vouch for the entire run of cable and be certain that it does not run through or under any insulation??
Is there RCD protection to the circuit, if so, what rating is the RCD?
you should perhaps read the links supplied and ask specific questions on aspects that you dont understand, we will help you to understand and you can do a safe job.