Xperia z3 not waterproof as advertised

i was until April an extremely proud owner of a z3,I bragged about phone to everyon but I refused to take pics underwater.in April I went to visit my mum and after countless videos and begging from my kids that the phone was meant to go underwater,I got into the shallow section of the pool myself not trusting my kids to take the phone in the water ,after making sure all the ports were securely closed i quickly took a pic underwater and jumped out,thereafter the phone started flickering and switched off....I took it into Altech Autopage and had phone booked in for repairs,after 1 month it was returned to me stated phone is BER.After calling Sony mobile,Sony repair centre and Altech Autopage was told the phone had liquid damage.i refuse to accept that.i did exactly what Sony and Sony Xperia z3 promised on all their adverti*****ts,take a pic underwater,now Sony tells me that the so called waterproof phone is not waterproof after all.i was careful ,made sure I did everything right yet still the water got in so all the advertising Sony is doing is false.i will not leave this till I am given a new handset as I refuse to be responsible for something that I know I wasn't negligent with