Water damaged iPhone reboots when I shut it off

I dropped my iPhone 6s in the start of a river earlier today, it was maybe half a foot in water and we picked it up aprox 10 seconds later. When we took it out the water it was still on (I had the camera app open) and I tested the speakers which didn't work for the next 5 minutes and shut it off about 10 minutes later. Everything was working fine after we took it out of the water, but I still shut it off to not cause shorts or further damages. As soon as I got home (15 mins after the water drop) I put it in rice. I left it in a sealed container filled with rice for about 9 hours until I went back to check up on it, by accident I turned it on somehow and everything was working perfectly, even the sound. The wifi, speakers, touch screen, everything was fine except for the lock button. So I tried turning it off through touch assist and noticed that as soon as I turned it off, it would reboot to the apple logo for 4-5 seconds and shut off, then it keeps repeating that until I press harder on the lock button/tap on the back of the phone for it to turn on again. I put it back in the rice container for it to dry more overnight, I turned it off but it keeps rebooting. It'll keep doing so until it runs out of battery. I think the lock button might be sticked, or maybe it's a software issue. Regardless I'm not too sure what to do or what's wrong with it? Do I have a chance at saving it, should I just replace the battery?

thank you !!