Waterproofing USB port
The new S7 phones with IP68 ratings seem to include a moisture sensor in the usb port. It will prevent charging if it detects any moisture. It's reportedly very sensitive.

Undoubtedly, this is also used to shut off any potential USB-OTG output, if the phone supports full OTG support. Not all phones have OTG, and if those that do, many do not power the port, requiring a y cable and external power. The S7 phones support full OTG, and even have a OTG adapter in the box (for migrating from an old phone. Neat).

Standard techniques like short circuit detection would still apply, and likely enabled by which-ever usb switching IC or PMIC Samsung is using (likely in-house based on my S5 generation device).