The latest Kindle Paperwhite is the first Kindle to come with a USB-C port, and according to Amazon it’s able to detect moisture and temporarily disable charging to help avoid problems.
There’s this help page at Amazon that talks about how to Resolve Liquid Detection Issues on Kindle ereaders.
Apparently if your Kindle detects liquid on the USB-C port, a notification will appear on the screen, and you will be unable to charge your Kindle via USB temporarily (they say you can still use wireless charging on the Kindle Paperwhite Signature Edition).
Amazon says you can still use your Kindle after getting a liquid detection notice, but you just won’t be able to charge it until the USB port is dry.
I tried to trigger the warning on my Kindle Paperwhite 5 by putting the USB-C port under running water while the device was turned on, and then I let the water sit in the USB port for about 30 seconds, but nothing happened.
The Kindle Paperwhite is IPX8-rated, meaning it’s waterproof for up to 60 minutes in 2 meters of water, so getting water on the USB-C port isn’t a problem, but you might encounter the liquid detection alert if it does get wet.
Amazon notes that the notification will appear intermittently as liquid evaporates from the USB-C port. They say to keep the cable unplugged and wait for the port to fully dry for up to 48 hours. See the help page at Amazon for more details.