It comes as a surprise to many boat owners to learn that the electrical systems aboard their boats are governed by no federal or state body. With few exceptions, boat builders, boat yards, marine electricians, and do-it-yourselfers in the United States are under no mandate to follow any specific electrical design or installation guidelines, and no license or certification is needed to be a marine electrician. Anyone, regardless of experience or training, can hang out a ‘Marine Electrician’ shingle and begin installing or repairing these systems. 

electric shock drowning
Sadly, electric shock drowning events occur each year.

The American Boat and Yacht Council (ABYC) publishes a phonebook-like tome, the “Standards and Technical Information Reports for Small Craft,” which includes several chapters dedicated specifically to marine electrical installations. These Standards, however, are purely voluntary where recreational craft are concerned. Keep this in mind as you read the remainder of this article. 

Only those who are current members of ABYC, and preferably possess an Electrical Certification, and agree to comply with the relevant published Standards, should be entrusted with carrying out electrical work aboard your vessel. 

Electric Shock Drowning Events Happen Every Year

In 2012 three cases of electrocution occurred over the Independence Day holiday. Tragically, they resulted in the deaths of four children, siblings Brayden and Alexandra Anderson (ages 8 and 13 respectively), Noah Winstead (10), and Nathan Lynam (11), and one adult, 26-year-old Jennifer Lankford. All of the events occurred on lakes, one in Tennessee and the two in Missouri. More recently, on April 20, 2017, three more cases occurred, in which 15-year old Carmen Johnson, 34-year-old Shelly Darling, and 41-year-old Elizabeth Whipple were all killed while swimming in Alabama’s Lake Tuscaloosa. In June 2017, five more people were killed at a water park in Turkey. 

Each year electrocution, in many cases more accurately referred to as electric shock drowning or ESD events such as these occur, and each year a call goes out within the marine industry to educate boat owners, marina managers, marine electricians and swimmers about the dangers associated with swimming around boats that are plugged into shore power, or other shore power devices such as electric boat lifts, water slides, or docks with shore power. Sadly, for these people, most of whom are children, and their families, it’s too late; however, it’s not too late for you to learn about these potentially disastrous scenarios and how to avoid them. 


You would be hard pressed to find an adult who is unfamiliar with the ubiquitous Ground Fault Circuit Interrupter or GFCI receptacle. Found in household kitchens, bathrooms, patios, and garages among other locations, and recommend by the ABYC for use in heads, galleys, engineering and bilge spaces, and on the weather decks of boats, they have no doubt saved countless lives since their introduction in the late 1960s. Requirements for GFIs have been part of the National Electric Code for over 50 years, with the first mandate being inspired by electrocutions caused by underwater lighting used in swimming pools.

While GFIs are fairly well-understood, there is yet another shore power safety device, one that was only introduced to the marine market within the last decade, that’s also worthy of attention. Known as an Electronic Leakage Circuit Interrupter or ELCI (sometimes referred to as RCDs or Residual Current Devices), it offers yet another level of protection from shore power faults, fire and electrocution, or ESD. Much like a common GFI receptacle (these have a comparatively low trip threshold of five milliamps, and as such are considered to be appropriate for protecting people, they represent “local” point of use protection), ELCIs remain in a state of equilibrium, allowing energy to flow, as long as the current on the hot and neutral wires, the two current-carrying conductors found in most AC electrical circuits, remains the same. 

electric shock drowning
GFCIs provide those aboard with electrocution protection. Galley, head, machinery spaces, and weather decks should all be covered by these.

As soon as current finds an alternative path back to its source (contrary to popular belief, electricity does not seek ground, it seeks to return to its origin; in this example likely the transformer at the head of the dock, via the water and earth), through a green safety ground wire, the water or a human, the imbalance trips the ELCIs (GFCI, RCD, etc.) circuit breaker and the power is turned off nearly instantly, often within 30-70 milliseconds.  

While technically deemed “equipment protection,” because of their comparatively high 30 milliamps trip threshold, the goal of ELCIs is to interrupt current flow quickly enough to prevent electrocution, electric shock drowning, or fire, and for the most part they do so very effectively. 

The adoption of the ABYC ELCI Standard was, much like the GFI, inspired by a number of electric shock drownings or ESDs. Different than a conventional electrocution, an ESD can, with comparatively little current flow, paralyze a swimmer’s voluntary muscle reflexes, causing him or her to drown, which only serves to mask the underlying electrically-related cause of death. 

Fresh or Salt, Does it Matter?

While it’s true that virtually all documented ESD cases have occurred in fresh water, the risk of swimming around docks and boats that are energized with shore power, in salt or fresh water, remains high. Some will say, “It can’t happen in salt water,” and I cringe each and every time I hear this. There are several reasons this “theory” represents dangerous folly. One, it’s impossible to determine the salinity level of a body of water before jumping in to cool off. In estuarial waters such as those on the Chesapeake Bay, salinity changes seasonally and even daily after heavy rains. 

Two, it’s impossible to rule out the potential for ESD or electrocution in seawater provided the current flow is high enough. Do you want to risk your life or the lives of your loved ones by testing this theory? Folks often ask me when is it okay to swim around docks, saying, ‘What if the vessel does have an ELCI?” or “The dock has a leakage warning system; is it okay then?” Or, “Can the water be tested before swimming?” 

Unfortunately, the answer is no to all of these scenarios for a variety of reasons, including and especially because faults occur in a split second, one minute the water is safe, and in the blink of an eye it’s deadly. Unless you can walk on water you can’t count on being able to get out of harm’s way quickly enough. Also, as wonderful as ELCIs and GFCIs are, they are not foolproof. 

In addition to the trip threshold, the primary difference between the ELCI and its cousin the GFCI, is the location in which it is installed. GFCI receptacles are installed where power is to be used, galley, head, etc, while ELCIs are installed where power enters the vessel, near the shore power receptacle. Think of it as a whole boat GFCI with some modifications. A primary shore power circuit breaker is already required for every shore power inlet, and in the case of an ELCI it is often installed either in conjunction with this breaker, or as a single combined unit, achieving the goals of over current protection and fault protection. It’s important to note that the presence of an ELCI does not negate the need for individual GFCIs, both are still required for ABYC compliance.

electric shock drowning
This shore cord shows over an ampere of fault current, almost four times the generally accepted threshold of 30 milliamps.

ELCIs got off to a rocky start when they were first introduced to the ABYC Standards and the marine industry in 2008. As is often the case, the intent preceded the hardware, and as a result the implementation was postponed for a couple of years. Now, however, proprietary marine ELCI circuit breakers are readily available from several manufacturers in a range of configurations. 

With few exceptions, new vessels that are built, or those that are being refit, to ABYC (or European CE and other) Standards must be equipped with ELCIs, and with good reason; they save lives by preventing electrocution, ESD, and fires. An ELCI can be added to virtually any vessel’s shore power system provided it is free of faults. Adding an ELCI to a vessel whose electrical system is faulty, where individual or collective faults exceed 30 mA, will simply result in tripped circuit breakers and no power aboard. Before an ELCI is retrofit to any vessel its leakage current must be measured, if it is close to or exceeds 30 mA the fault must be identified and corrected.

Dockside Protection

A growing number of marinas have taken on the responsibility, or have been compelled to do so, of equipping their shore power systems with ground fault protection (GFP) devices, which are similar to ELCIs, further reducing the likelihood of electrocution and ESD. As worthy as the effort is, many of these marinas or their contractors have selected unrealistically low trip threshold devices of just 5 mA (they can be as high as 30 mA and still be compliant), and thus frequent tripping at these marinas has become commonplace, and therefore very frustrating for boat owners. 

It’s impossible to determine, without carrying out an evaluation of the electrical system, if these trips are the result of a genuine and potentially life-threatening fault, or simply the result of either the aggregation of small, otherwise non-threatening, faults or GFPs with an exceptionally low threshold. Attempting to ferret out collective faults, and maintain them below this threshold, is virtually impossible, and even when it can be achieved, it’s rarely a long-lasting solution. Ideally, each inlet on each pedestal should be individually protected by a 30 mA GFP; if it trips the fault is almost certainly genuine.

electric shock drowning
In Europe shore power pedestals have included ground fault protection for years.

One genuine boat owner solution to this problem involves the installation of a shore power transformer, also known as an isolation or polarization transformer. Electrically, transformers behave as if they are a source of power, and because electricity always seeks to return to its source, faults travel to it instead of through the water, thereby preventing dockside GFPs from tripping. However, those considering the installation of a transformer must, in addition to the expense, keep in mind that it can also mask a genuine underlying problem. Transformers should be installed only after the vessel’s electrical system has been deemed safe by an ABYC certified electrician. 

If you intend to go the transformer route, consider that one with boosting capability will correct otherwise low dockside voltage, protecting voltage-sensitive appliances such as refrigerators and air-conditioning systems.

You might ask, “What about divers? I see them in the water in marinas all the time and they don’t get electrocuted.” Whenever I encounter one on a dock, and that’s often, I make it a point of asking, “Do you ever get shocked or feel a tingle?” Without exception everyone has said “yes,” a few have told me they can feel electricity coursing through their dental fillings. A drysuit or even wetsuit do offer some protection against electrocution and ESD, which is why these folks probably haven’t become victims, and most do their work in salt water, which does to an extent mitigate the effects of current flow. They do this work at their own risk, hopefully knowing the hazards, a far different scenario from your child frolicking in the water on a seemingly carefree summer day. 

Simply put, never swim around docks equipped with shore power in fresh or salt water. There are no exceptions to this rule. 

About the Author: Steve D'Antonio is a marine systems consultant, offering services to boat buyers, owners, and the marine industry, as well as an author and photographer. He is an ABYC-certified master technician.