USB-C really does not make sense for such a device. It's significantly too bulky and is hard to get water proof
I doubt that modern smart phones are waterproof. Who would trust use their smartphone while showering or being in a bathtube (including submerging the smartphone a few centimeters into the water)?
I remember when the iPhone 7 had just come out (the first waterproof iPhone), a friend bought one and then went on a cruise. On a shore excursion he was at the docks and saw some cool fish. He dunked his phone in the water to take some cool photos. Everyone looked at him like he was a mad man, dunking his iPhone in the water just to take some pictures.