Water detection via software is basically checking if any pins in the port are crossed when they shouldn’t be. Check the port to see if all the pins are straight. If the cable is from apple, just take the phone to apple together with the cable; chances are they’ll either replace the port or just give you an new iphone. They’ll see that it’s not water damaged (if what you say is true) because there are physical markers that change color inside of the iphone on contact with water.