I don't know what will happen in this case, but one of the first things I did when we bought our present boat was test every plug
with one of those little circuit testers to make sure the plugs were wired properly. Since our boat was originally 220V as delivered from the factory, I wanted to be sure whoever rewired it (and anyone who diddled with the wiring
since then) did things correctly. Easy and cheap insurance
Some of the testers have a little button to cause a ground fault, which is quite handy.