I had a couple of times this went off and my charging port was surely dry. It turn out the usb c cable I had was the actual cause of my problem. I think it might have just been dirty but I did not clean it I just replaced it with a new one.
I've seen this message once... Not sure what caused it myself as I was nowhere near water. It was a hot day so I assumed some moisture might have built up in the charging port or the cable connection. I just took a dry microfiber towel wiped it and used a different cable.