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The Hidden Danger of Swimming in Marinas

Stray electrical currents can pose serious threats in the water where boats are connected to shore power.

Have youever wondered why marinas post No Swimming signs? Yes, there are dangers from boat traffic, and from surface pollution thats sometimes concentrated in marina waters, but one of the main reasons for the signs is the possibility that a boat with faulty wiring or grounding might be leaking electrical current into the surrounding water. In many accident studies and reports, as many as 26 percent of all boats in marinas are leaking some amount of current into the surrounding water.

In just the past year there have been several fatalities involving people swimming or entering the water around boats when strong electrical currents are present. In all of the cases, the vessels were docked in marinas, and either the swimmers own boats or the surrounding vessels were connected to shore power. All of these accidents we

re in fresh water, but this does not rule out similar dangers in saltwater marinas.

A standard yacht insurance policy includes liability coverage to defend and protect the boatowner if an accident occurs, but a death or serious injury involving your boat or your shore power connection is a horrible thing to contemplate. In this case, an ounce of prevention is definitely worth a pound of cure.

One piece of equipment that can help prevent such accidents is the Electrical Leakage Circuit Interrupter (ELCI), which made its way into the 2010 American Boat and Yacht Council (ABYC) electrical standards, and in the same year became a requirement for all 120/240VAC systems within the National Marine Manufacturers Association (NMMA) certification program. You will notice the ELCI on 2010 and newer model boats. Its much like a clamp-on ammeter you would buy at your local hardware store, and will most likely be installed at the main 120/240VAC panel with its own breaker.

The ELCI is a residual current device that detects leaking current and disconnects all ungrounded 120/240VAC live conductors from the supply source. On an alternating-current system the power alternates between the hot and neutral conductors. If everything is installed correctly, the current between these conductors or wires should be the same. The ELCI will read any difference between the conductors, and if this difference is great enough, it will trip the breaker. Essentially, it is detecting any pos

sible stray current and shutting down the shore power entering the boat.

Shore power is not necessarily the only source of 120/240VAC power on your vessel. Your generator or inverter can cause the same problems if theres improper or damaged wiring on your vessel. It is strongly recommended that you have your vessel inspected and tested for any issues. You can start by contacting a certified ABYC electrical technician to have your vessel and your neighboring vessels tested. Buy high limits of liability to protect yourself in the event of an accident, alert your guests to the dangers of electrical current in the water and its potential causes and remember why its not safe to swim in marina waters.

By: Marc Nugent

B.S.E., A.M.S.

Manitou Boatworks & Engineering

Manitou Boatworks & Engineering specializes in Standards, Marine Surveying and Consulting