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Author Topic:   Risk of Low Voltage Electrocution from Swimming in Marina
jimh posted 07-01-2015 01:29 PM ET (US)   Profile for jimh   Send Email to jimh  
On August 15, 2011 in Traverse City, Michigan, Michael Knudsen, an 18-year-old boy, jumped into the water near the F-Dock of the Duncan Clinch municipal marina, despite the presence of signage prohibiting swimming. Due to muscle paralysis from a leakage of electrical current from the marina 120-VAC power wiring, the boy could not swim, and he subsequently drowned. This unfortunate accidental death became the issue of a lawsuit brought by one of the dead boy's companions, who also jumped into the water but was able to get out safely, and by the representatives of the estate of the dead boy. A legal negligence action charged a number of parties as responsible, including:

--the city of Traverse City and several of its officials

--the marina harbor master

--the contractors that performed the construction or renovation of the electrical system

--the engineering firms that designed the marina electrical system

--and several individuals of those companies

This legal action resulted in a trial court decision in favor of some of the defendants by virtue of their immunity by law; an appeal of the trial court decision was made to the Michigan Court of Appeals. That court rendered an opinion which is published at

The Court of Appeals opinion makes available a good summary of the events involved in the accident, and some details of the electrical problems that produced the leakage of current into the water. A reading of the opinion regarding the electrical circuits and the danger they posed to anyone in the water is instructive. The legal questions at issue are perhaps also interesting, but not as much as the basic facts of the case regarding the presence of a extreme danger to anyone getting into the water in the Duncan Clinch marina that day.

This unfortunate accident may be a good reminder to anyone thinking about swimming in a marina where there is 120-VAC electrical wiring. There is the potential for fatal harm to come to anyone in the water if there is leakage of electrical current. Keep this risk in mind if you have any thoughts about swimming in a marina this summer.

Jefecinco posted 07-01-2015 07:17 PM ET (US)     Profile for Jefecinco  Send Email to Jefecinco     
These deaths occur with alarming frequency all over the country. I simply assume there is stray current present at every marina we visit. If the shore power or lighting wiring is not faulty then the wiring or isolation system of at least one boat in the marina will be faulty.

I don't know if it is true, but I heard of an incident on, I believe, Lake Meade when a swimmer near the swim platform of a boat drowned due to paralysis caused by stray current from the generator power on the boat.


jimh posted 07-01-2015 11:40 PM ET (US)     Profile for jimh  Send Email to jimh     
Butch makes a very valid point: even if the wiring of the marina is completely compliant and in perfect condition, the wiring of a boat--maybe even your own boat--in the marina could create a low-voltage electrocution hazard for anyone in the water near that boat
jimh posted 07-02-2015 09:52 AM ET (US)     Profile for jimh  Send Email to jimh     
In the legal opinion I cited above in regard to this marina electrical defect, a mention is made of the conformance of the electrical system to the "1990 NEC specification." I believe that in 2011 and then again in 2014 the National Electrical Code regarding marina power distribution was significantly updated. Recently constructed or renovated marinas most likely are conforming to the newer 2011 or 2014 requirements.

Here is a secondary source of NEC Article 555 revised to 2014.

David Pendleton posted 07-02-2015 02:44 PM ET (US)     Profile for David Pendleton  Send Email to David Pendleton     
It should also be noted, for anyone researching this topic, that this is strictly a freshwater phenomenon.
Jefecinco posted 07-02-2015 07:18 PM ET (US)     Profile for Jefecinco  Send Email to Jefecinco     

I admit my ignorance. Why can't the described situation occur in brackish or salt water?


dfmcintyre posted 07-02-2015 09:22 PM ET (US)     Profile for dfmcintyre  Send Email to dfmcintyre     
Happened here in Port Huron, at the city marina to a friend's son. Tragic.
djahncke posted 07-02-2015 10:59 PM ET (US)     Profile for djahncke  Send Email to djahncke     
The reason this happens in fresh water is that the human body is a better conductor of electricity than fresh water. So most of the electricity takes the path of least resistance through the body causing paralysis.

Saltwater is a better conductor than the human body so in saltwater most of the electricity flows around and not through the body. Result is not enough current flowing through the body to cause paralysis.

David Pendleton posted 07-03-2015 12:00 AM ET (US)     Profile for David Pendleton  Send Email to David Pendleton     
As it happens, there is an article about this very topic in today's Great Lakes Scuttlebut: what-every-boater-needs-to-know-about-electric-shock-drowning./

Jefecinco posted 07-03-2015 06:11 PM ET (US)     Profile for Jefecinco  Send Email to Jefecinco     
So, am I correct in guessing that the risk in brackish water is dependent upon HOW brackish the water is? Lacking that knowledge I going to assume brackish water is as deadly as fresh.

Seems to me the alternative assumption would be risky??

Would it be fair to say the risk is not limited to freshwater only?


jimh posted 07-05-2015 01:18 PM ET (US)     Profile for jimh  Send Email to jimh     
I found an article (hyperlinked below) that discusses the risk of electrocution as a function of voltages and currents, where they are applied, and other various factors that ought to be considered. For readers who want to calculate the conductivity in the water that will be necessary to cause a voltage gradient in the water to tend to pass through the water instead of through a human body, some of the data in this article might be useful for making such a calculation. Personally, if there is electrical current leaking into the water from a 120-VAC source, I am not inclined to dismiss the risk of electrocution on the basis of the salinity of the water. See:

wezie posted 07-09-2015 12:10 PM ET (US)     Profile for wezie    
As I understand, the term Brackish is subjective. As you stated, how much salt, is the question.
As rains occur or not, so the salinity of bays and estuaries change.
In a private (individually owned dock) environment, we might be comfortable with our electrical work and precautions. In anything else, I guess brackish water is really fresh water for electrical safety rules.
David Pendleton posted 07-10-2015 01:49 AM ET (US)     Profile for David Pendleton  Send Email to David Pendleton     
Here's a thought: don't swim in any marina.
Jefecinco posted 07-10-2015 08:42 AM ET (US)     Profile for Jefecinco  Send Email to Jefecinco     
That is absolutely my policy.


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