Blinking battery symbol after wet

First, rice is a myth. While the theory makes sense, it just creates a huge mess inside the device. If the device was fully submersed in water then the battery likely needs to be replaced. It’s also possible the screen needs to be replaced as well. These are the two common things that needs to be replaced in water damaged devices.

What you really need to do is get the device opened up and get any water out of the device and clean up any corrosion that may be starting. If you don’t have the skills or tools to do so take it to a local repair shop that does water damage recovery work.