A GFCI on the AC line is usually the first like of defense. Not sure if a standard EVSE has this.
The GFCI senses the current going down one wire and coming back on the other. If the difference is more than a tiny amount (indicating an unintended current path), it cuts the AC power.
The second line of defense is for the charger output to be isolated from the input, which most are.
People use power on boats all the time. The real hazard is if your electronics get wet and fail, possibly starting a fire.
"One test is worth a thousand opinions"