My wife did this to her iPhone.
She grabbed it, and it was only under for a few seconds, but that was enough. We had it in rice, then in dryrite for a few days. Initially it got to the point where it wouldn't turn in and the LED light (flash) wouldn't turn off.
Sent it to Apple, and they got it to turn on, but didn't do anything about the flash. Sent it back again (since they never completed the repair) and they ended up swapping out a new one. One of the water sensors was triggered (one wasn't) but they never charged us for the repair. I can't guarantee the same will happen to you.