Samsung Mobiles - Samsung s8 plus water resistant fraud

I have purchased Samsung s* plus *** gb version mobile from Croma Ahmedabad on ** August **** by watching their commercial advertisement of mobile being water proof when a person jumps in to swimming pool with device, recently my * years son has accidentally dropped mobile in to bucket of water for hardly one minute, post which mobile was dead. I took it to the nearest service center at Gandhinagar where executive without opening the mobile told me story that if mobile is water damaged it can not be covered under warranty. I further complain to there customer care division whereas they told me that without opening a mobile service center can not commit any thing. When Samsung itself is accepting that without opening device it can not be claimed of warranty void or not then how service center is making frauds.