WASHINGTON- The Coast Guard Auxiliary suggests you have your dock inspected periodically for bad wires and loose grounds. The same goes for your boat. Any time a person swims around a dock or boat where there is AC power, electrical shock could occur. A boat plugged into shore power with a short on board is dangerous and the owner may not be aware of it. AC current may enter the bonding system if an AC ground becomes disconnected then electrical current can enter the water by way of a bonded thru hull fitting. The boat dock can also develop a short and create a potential life threatening hazard. Some drowning were discovered to be from electrical shock.
Electrical discharge into salt water from a boat is not as dangerous as discharge into fresh water. The reason being, salt water is a better conductor and will allow the current to flow to the bottom or some other grounded metal around the dock or to the neighbors boat while fresh water being less conductive will form an electrified field around the boat. Many marinas have stopped allowing swimming around docks because of these hazards.
The American Boating Association
PO Box 690
New Market, MD 21774