possible hardware damage on iphone 12

I took it out on a boat trip today morning, assuming it would be fine because it was still on the boat. However, it is very possible that some ocean water was at a small leak where my phone was. It was very little i believe, but now my face id doesnt work and the bottom half of my phone isnt touch screen anymore. i had a case that stopped it and two life jackets wrapped around it. if it is hardware damage, is there anything i can do at all at home? but otherwise how much does it generally cost to fix? thank you so much