I did this once is a brothel in Thornton Heath probably 7+ years ago. The EE lady talked me into it some how, she disappeared leaving me thinking WTF have I committed to, came back with a 2l bottle of water which she drank put towels under me then eventually pissed on me. I didn't enjoy the pissing but the sex after with her pissy pussy and me obviously covered in piss was amazingly dirty. The reality struck after I had blown. First problem was their was no shower facility so I had to clean up as best I could using wet wipes then shower at home.. nice...
Next the towels obviously hadn't caught everything so floor was covered in piss (not my problem), finally the maid (a small Chinese guy want to see the weird guy into WS)...
My advice, find a specialist and make sure they have facilities to facilitate this. Finally be aware of the risks, what I didn't know is Chlamydia and gonorrhoea can both be passed on relatively commonly by watersports
...