In theory, since the battery and engine are sealed, it would be more resistant, NASA's mars robots worked for decades in mars with no major reliability problems, in ww2 people experimented with electrical transmission in tanks, so that they could in theory be plugged into another tank with a diesel engine providing power and drive through the floor of a river without it's diesel gassing the crew, they didn't do this due to the huge costs of a engine needing copper in a war.
The battery is sealed, but if exposed to water, it could be a major explosion and fire risk, just pierce your old phone's battery and drop some water on it.
The main problem is the wiring and electronic components, if the this thing was just a husk with a electric engine and battery, it could work for decades with no problems, but full of complex stuff, cameras and sensors? I don't think so.