Do you have this gap?

[Rukbat]

IP68 protects against about 2psi of water pressure, so if you gently pour water in the middle of the screen and it oozes to the edges you're fine. But if you put it under a tap with, probably, about 15psi at the faucet, plus whatever it gains from falling, it might get into the phone. (A waterproof phone would be guaranteed against water damage. The Nextel 225 was. (And that's about the only cellphone that ever was.)