Hello and sorry you're having problems. If the device is not taking a charge, it could very well be due to water shorting out circuit board traces inside of the device- and that would require either long periods of drying, and/or repairs.
However, there is a reset for the Kindle that can often fix problems like this. Please try the following both as a TEST, and an attempt at a fix.
Press and hold the power button on the Kindle for 40 FULL seconds, then release and wait a full minute for it to reboot (do no press anything else within that minute).
If this does not cure the issue, try that reset up to THREE TIMES and wait the full minute to see if it reboots.
If you're still running into problems, then try plugging the Kindle into the charger for 15 minutes, then eject it and try the reboot a couple of more times.
If the device still does not work beyond that, then please reply back with the Model of the Kindle and also the AGE of the unit- and we can proceed.