Hi @tasman
Sorry to hear about your iPhone but we need to work on this one fast!
First turn it off and DONT put it in rice and if you have distilled water, water the iPhone down to dilute the salt water as salt water is very corrosive to electronics!
Second take the screen off and unplug the battery
And dowse the logic board with isopropyl alcohol
If you can’t do this I would take it to a repair shop
Just don’t try and turn it back on until the problem has been resolved
If you want to do this your self I would order a new screen and battery,but I would take it to a repair shop as they have all the equipment to sort your issue out properly
Hopefully this helps
Thanks:-)