It appears that Apple has added a feature in iOS 10 that can detect if there is liquid in your device's Lightning connector. As seen in the above images, posted to Reddit by u/lucioghosty, if liquid is detected, iOS 10 warns you to keep the port clear until it dries.
The alert takes up the full screen, and apparently stays until you either disconnect whatever Lightning is plugged into the port, or you tap the Ignore button. Note that tapping Ignore pops up another warning saying, "this may damage your iPhone."