As you know water and electronics and electricity are not a good mix.
The impurities in the water causes corrosion and provides circuit paths for the electricity which were not in the device’s operating design and could damage the components.
Rice does not fix the problems caused by corrosion.
rice is for dinner, not repair
First do not turn on your device and then you need to remove the battery as soon as possible from the device to minimize any further damage.
Then you need to dis-assemble the rest of the device and clean all the affected parts using Isopropyl Alcohol 99%+ (available from electronics parts stores) to remove all traces of corrosion and water. Do not use "rubbing alcohol" as in some cases this is only 70% IPA or less, can contain scents and is not as effective. If you do have to use it, check the label to verify the amount of IPA. The higher the % the better
Here is a link that in general describes the process.
Electronics Water Damage
As always with electronics, especially surface mounted PCBs be gentle when handling and especially when brushing away the corrosion. You do not want to remove any components from the board.
Hopefully after you have done all this the device might possibly work correctly again.
Here’s a link to a teardown video of your device which may be of some help.
If this process seems too daunting, take your device to a reputable, professional electronics repair service, experienced in liquid damage repair and ask for a quote for a repair. If you decide to do this, do it sooner than later.