New Shore Power Receptacles and the Dangers of Electric Shock Drowning

The water is starting to warm up in our local waters but before you jump in, there are a few things you should know about Electric Shock Drowning (ESD) and the dangers of swimming in or near marinas that offer AC electrical services.  ESD can occur in both salt and fresh water however, the risk is greater in fresh water which is almost 70X more resistive than salt water.  In fresh water, the human body is more conductive than the water so the electrical current flows through the human body instead of the water.  Saltwater has a low resistance and tends to divert the electrical current around the body, but not in all cases.  Docks and marinas with no power pose no danger from electrical shock.

The Electrical Safety Foundation International. Electric current in the water causes paralysis in the muscles which leads to drowning.  According to the Electrical Safety Foundation International, it only takes 10 milliamps or 1/50th the amount used by a 60 watt lightbulb.  There is no visible warning and, quite often, people are incapacitated jumping in to save someone who is already in the water.  It’s not just swimming, ESD can happen during any in-water activity such as cleaning the hull, inspecting zincs or props, children or pets falling off a dock or even climbing out of the water using a metal ladder on the swim grid.

So what can you do to protect yourself?  There are two sides to this socket, the marina and your boat.  On the marina side, ensure that where you moor is up-to-date with the Canadian Electrical Code (or in the US, the National Electrical Code, specifically Article 555) that addresses safety issues due to stray electrical current in and around marinas and boatyards.   The requirements for ground fault circuit interrupter protection of class A type receptacles has been extended to all receptacles installed on fixed or floating piers in harbours.

A Ground Fault Circuit Interrupter (GFCI) is an electrical device that trips an electrical circuit when it detects ground faults or leakage currents.  Mostly likely you will have one of these installed in your home in the bathroom and is recognized by the red reset button.  They are often located in areas where water and electricity are in close proximity such as your kitchen, bathroom, basement or outside.  Many marinas are now upgrading the power pedestals, on the dock, to include GFCI protection.  In most cases, you can plug in your shore power cord and carry on as normal however, some marine inverters will sense an imbalance during the syncing phase causing the breaker to trip.  The same thing can be caused by older galvanic isolators, marine battery chargers or non-marine appliances where the neutral is tied to the ground.

On the boat side, you need to understand what causes ground faults?  The top three causes for ground faults are electric water heaters, old battery chargers, and neutral to ground ties at a point in the boat’s electrical circuitry other than a source of AC power.

On boats, only sources of AC power should offer a ground to neutral connection.  For example, a generator, an inverter (when inverting), or an isolation transformer. Otherwise no ground to neutral connection should exist. Many land-based electricians inadvertently apply their on-land wiring protocol and tie the ground and neutral bus. As more AC loads are turned on, there is a chance that some of the current intended for the neutral will also use the grounding system.

A combination of these factors, plus some bad dock wiring, increases the probability that some AC current will enter the water via a through-hull or bonded underwater connection, therefore creating a potentially lethal situation for swimmers.

To protect your boat, you can install an Equipment Leakage Circuit Interrupter (ELCI) to provide overcurrent protection for the shore power system.  ABYC standards were updated to include section E-11.11 that states, “An ELCI shall be installed with or in addition to the main shore power disconnect circuit breaker(s) or at the additional overcurrent protection whichever is closer to the shore power connection.” Newer boats will be equipped with an ELCI breaker, to confirm this, you will see the ELCI breaker on the A/C breaker panel or near the boat’s shore power inlet.  It should be labelled “ELCI Breaker” and have a TEST button.  Depending on the size of the breaker (30 or 50 amps) they cost about $100 and can be added to your existing A/C panel or in a separate enclosure close to your shore power inlet.

The second thing you can do is to have your boat inspected by an ABYC Certified Electrical Technician. A knowledgeable technician will be able test the individual AC circuits and measure for any imbalance of current in the circuit.

Ed Sherman, Vice President and Education director at the ABYC says “Non-marine electricians will often innocently wire boats as they would a home, without knowing that the wiring configuration requirement on boats is quite different from homes.”  Your boat is in a damp environment and subject to vibration, household wire is not designed for this setting.  Even marine-rated wire that is not supported along the entire length of the run will break causing leakage. 

Isolation Transformer. In last month’s Tech Talk article, we discussed the installation of an isolation transformer to enhance electrical safety for offshore boaters and mitigate galvanic corrosion issues related to ground currents from shore.  As a bonus, they also eliminate the possibility of tripping a dock GFCI breaker.  If the isolation transformer is installed within 3 meters of the shore power inlet then an ELCI breaker is not required to be ABYC compliant.

Electricity can enter the water from an electric fault in the marina’s wiring or from a boat connected to shore power.  If the leak is from the boat it can also be intermittent and only happen when a particular device is turned on.  Both ELCIs and GFCIs measure current flow in the hot and neutral wires and immediately switch the electricity off if an imbalance of current flow is detected.  Utilizing both of these devices will help protect you and your fellow boaters from the dangerous consequences of ESD.

The ESD Prevention Association has a very informative website at

About the author: Jeff Cote is the owner of Pacific Yacht Systems, a full service shop delivering marine electrical and navigation solutions for recreational boats. Visit their website and blog for info and articles on marine electrical systems, projects and more: