Danger! Do not swim in a Marina!
On June 27th, 2005 at a marina on Cave Run Lake near Morehead Kentucky a woman drowned as a result of being electrocuted while swimming off a houseboat. A second swimmer also received apparent electrical burns. The houseboat air conditioner is believed to be the source of the electrical current leaking through the water.
A similar incident occurred at a dock in a marina on the Willamette River's Multnoma Channel near Portland Oregon. Read the story about Lucas Ritz. Link to newsletter that contains story.
What happened?
There have been other incidents like this where faulty wiring or equipment have leaked current into the surrounding water through a submerged metal part of the boat such as the boats I/O drive or thru-hull fitting. This phenomenon only happens in fresh water marinas. There have been no reports of this ever happening in salt water. Salt water conducts electricity better than the human body. In fresh water the opposite is true.
How to Prevent
A properly wired boat, per ABYC(American Boat & Yacht Council) standards, will have the green grounding wire connected to the battery negative which is in common with the engine and other metal parts of the boat. If there is an electrical fault there should be enough current to ground to trip the breaker. Theoretically it is possible to leak enough current out of the boat to cause injury to a swimmer without tripping the breaker. GFIs (Ground Fault Interrupters) should be installed on the boat on all circuits including battery chargers, even though this is not currently required by the ABYC.
A Ground Fault Interrupter (GFI) properly installed at the dock power pedestal would prevent this from happening but is not required by National Electrical Code. They have been installed and proven to work despite some skepticism that there would be nuisance trips in a marina environment. I think this would be the ultimate protection because this would remove power if the shore power cord is accidentally dropped into the water. If the shore power cable is in excellent condition this would be a non event, but if the insulation is even slightly damaged current could flow into the surrounding water. Having a properly wired boat does nothing to protect against faults between shore and the boat's main electrical panel.
What Marinas can do
The marina can install monitoring equipment such as Marina Guard. This works similar to a Ground Fault Interrupter except it provides a warning instead of shutting off power to the offending device.
https://www.mikeholt.com/mojonewsarchive/SV-HTML/HTML/Hot-Marina-Lethal-AC-Ground-Faults~20031117.htmWhat should I Do?
Do not swim in any fresh water marina because you do not have any control over how shore power or other boats are wired.
Don't forget to test your GFI after a power surge or a lightning storm. If the electronics inside are fried, you are unprotected. Newer units are made to "fail safe" and will not work at all if damaged.
To
read more: Other documented cases can be found at: The
case of the Hot Marina ,
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