Water alone is a very poor conductor of electricity, especially at the volts and amps from an EV charger. Also, the port is well protected and, in a sense, not directly connected to the high amperage battery packs. The AC voltage and current goes through an inverter that converts it into the proper DC voltage and current. In other words, you can’t get the high DC amps at the charging port. There is also a few fail safes that protect you and the system. The manufacturer would advise against it but they do so to protect them selves in case there is a malfunction or a broken defective charger plug or cord.