Okay, I don't think I even want to know what possessed you to put your phone in water. Just know that's always a bad idea, okay?
First things first, do not turn on the phone or attempt to charge it. You'll need to disassemble it and clean it with 90% or higher concentration of isopropyl (rubbing) alcohol. Use this guide to take it apart.
[link|https://www.nadiemellamagallina.com/en/manuales/smartphones-1/lg-11/lg-g8s-thinq-1128/pantalla-completa-9954|Manuales / LG G8s ThinQ / Fullscreen|new_window=true]
Read through this guide to handling water damage; it's written for an iPhone but is every bit applicable to any phone that's gotten wet.
[guide|95280|iPhone Liquid Damage Repair - iFixit Repair Guide|new_window=true]
Batteries and screens are very susceptible to liquid damage so if I were you I'd plan on replacing both. However, it wouldn't hurt to start with a new battery and see what happens once it's been cleaned. If you can get any sign of life with the new battery but still don't have a display, then replacing the screen would be the next step.