Apple falsified water resistant feature on iPhone xs

I bought an iPhone Xs on the 24th of November 2018 at Telkom, Menlyn. My phone fell in water less than 30cm deep and was in there for about less than 10 seconds. I quickly took it out and dried it and went to the Telkom shop at Highveld Mall in Witbank and the guy there said that he cant help me my phone is dead. I told him about the water resistant feature in the phone and he said to me that they're all lies and a demo phone is used in the videos. My phone is not switching on, and the indicator is not red. I need an explaining as to why its acting up when it has IP68 which means it can be in water less than 2meters deep for no more than 30min. I'm really disappointed in both Telkom and Apple. I wouldn't advise anyone to believe whatever features Apple claims to have on their phones