What You Need To Know About Electric Shock Drowning (ESD)
If the dock you are jumping off of or those around it are electrified, don't leap.
Over Fourth of July weekend last year, Alexa Anderson, 13, and her brother, Brayden Anderson, 8, were swimming near a private dock in the Lake of the Ozarks in Missouri when they started to scream. By the time the siblings were pulled from the lake, they were unresponsive. Their parents performed CPR, but both children were pronounced dead after being transported to a nearby hospital.About two hours later, Noah Winstead, a 10-year-old boy, died in a similar manner at Cherokee Lake, near Knoxville, Tennessee, and Noah's friend, 11-year-old Nate Parker Lynam, was pulled from the water and resuscitated but died early the following evening. According to local press reports, seven other swimmers were injured that day near where Noah died. These were not drowning victims. In all of these cases, 120-volt AC (alternating current) leakage from nearby boats or docks electrocuted or incapacitated swimmers in fresh water. This little-known and too-often-unidentified killer is called Electric Shock Drowning, or ESD, and these deaths and injuries were entirely preventable.
If you grew up swimming off docks in freshwater lakes, it can be hard to get your mind around ESD. But several decades ago even the most sophisticated boats only had a battery to start the engine and to run a VHF radio. We didn't have lights and boat lifts on the docks, or water heaters and air conditioners on the boats. As often as not, we took our batteries in to the garage to charge them. In the past couple of decades, we've brought AC electricity and water together in a way we never have before. If the electrical system has been set up correctly with the proper failsafes, there is no danger. But if even minute amounts of electricity leak into fresh water, it can be lethal.
So how does that current get into the water? And what do you need to do to prevent ESD?
Photo credit: David Rifkin
Fresh Water + Alternating Current = Danger
In a properly functioning electrical system, all of the 120-volt AC current that goes into the boat through your shore power cable returns to its source -- the transformer ashore or on the dock where it originated. For any of that current to wind up in the water, three things have to happen.
- Electrical fault. Somewhere current must be escaping from the system, through a short circuit or a wiring problem on the boat or on the dock that allows current to find another path back to its source by traveling through the water.
- AC safety ground fault. Electrical systems are designed to deal with such stray currents by offering them a low resistance pathway back to their source through the green "grounding" wire. In doing so, the current from a fault or short typically trips a circuit breaker to remove the danger. But if the AC grounding system itself is compromised, which can happen if the wire has been damaged or connections have become corroded somewhere between the boat and the transformer, then stray electricity has only one path back to its source -- through the water.
- No ground fault protection. If some current is returning to its source through the water, then there will be a slight but detectable difference between the amount of current traveling to the boat and returning from it. Ground Fault Circuit Interrupters (GFCIs) like those required in bathrooms ashore to prevent electrocution are designed to detect a 50 or 100 milliamp difference and shut down the electricity within 100 milliseconds. If the circuit does not have a GFCI in it (or an ELCI -- Equipment Leakage Circuit Interrupter which are fitted in the boat's AC electrical system on newer boats), then there is nothing to stop the electricity from continuing to flow into the water.
Physical effects of AC current passing directly through the body:
Current level
Probable Effects On Human Body
1 mA
Perception level. Slight tingling sensation. Still dangerous under certain conditions.
5 mA
Slight shock felt; not painful but disturbing. Average individual can let go. However, strong involuntary reactions to shocks in this range may lead to injuries.
6-16 mA
Painful shock, begin to lose muscular control. Commonly referred to as the freezing current or let-go range.
17-99 mA
Extreme pain, respiratory arrest, severe muscular contractions . Individual cannot let go of an electrified object. Death is possible.
100-2,000 mA
Ventricular fibrillation (uneven, uncoordinated pumping of heart.) Muscular contraction and nerve damage begin to occur. Death is likely.
2,000+ mA
Cardiac arrest, internal organ damage, and severe burns. Death is probable.
Source: OSHA
What You Can Do
ESD has become a hazard because boaters want to take their 120-volt goodies and gadgets along with them when they go out on the water. There's nothing wrong with that, so long as the boat owner takes responsibility to have the AC system installed correctly and to maintain it, marina and private dock owners wire their docks correctly and check them regularly, and all of us understand what to do to as a boat owner, dock owner, swimmer, or rescuer.
IN GENERAL:
- ESD victims are good candidates for successful Cardiopulmonary Resuscitation (CPR). Learn to perform CPR and maintain your training.
- To retrieve a person in the water, reach, throw, and row, but don't go.
- Tell others about ESD. Most people have never heard of it and are unaware of the danger.
- Make sure your children understand the importance of not swimming anywhere there could be electricity. Don't let them roughhouse on docks. Tell them what to do if they feel a tingling or shock in the water (see below).
Photo credit Justin Baeder
IN MARINAS:
- NEVER swim within 100 yards of any freshwater marina or boatyard.
- Talk to marina owners or operators about the danger of ESD . Ask your marina operator to prohibit swimming at their facility and post signs.
- Ask marina operators if they are aware of and following the guidelines from NFPA 303 (Fire Protection Standard for Marinas and Boatyards) and National Electric Code (NEC) 555.
- Have your boat tested once a year to see if it is leaking electricity, or buy a clamp mete and test it yourself. If you find any problems, have your boat inspected by a qualified electrician trained to ABYC standards.
- Have a qualified ABYC electrician install an ELCI on your boat (refer them to the ABYC E-11 Standard) or use a GFCI in the shore power cord. As an alternative, install an isolation transformer on the boat.
- Test the GFCI/ELCI at least once a month or per the manufacturer's specifications.
- Do NOT do your own 120-volt AC electrical work on a boat or hire an electrician who is not familiar with ABYC standards to do it. Many of the problems that lead to an electrical fault on the boat result from the differences between shore and boat electrical systems and standards.
- DO NOT use common household extension cords for providing shore power to your boat. Use, and encourage other boaters to use, shore power cords built to UL standards, ideally with a GFCI built in.
- NEVER dive on your boat to work on underwater fittings when it is plugged in to shore power, even in saltwater.
- NEVER swim within 100 yards of ANY dock using electrical power!
- If you have not electrified your dock or put an AC system on your boat, weigh the risks carefully before doing so.
- If you need electricity on your dock, hire a licensed electrician and make sure the wiring meets the requirements in NFPA 303 and NEC 555. If your dock is already wired, hire an electrician to check that it was done properly. Because docks are exposed to the elements, their electrical systems should be inspected at least once a year.
- Exercise your GFCIs/ELCIs as recommended by the manufacturer.
- If you normally run a power cord from your house or garage to charge your batteries, make sure the outlet has a GFCI and include a GFCI somewhere in the shore power cord.
- NEVER swim off your dock without shutting down all shore power to the boat and the dock.
- Even if you adhere to all of these rules, nearby docks can still present a shock hazard. Educate your neighbors and work together with them to make the waterfront safe
- DO NOT follow your instinct to swim toward the dock!
- SHOUT! Drowning victims cannot speak, let alone shout. Let everyone know what's happening so they'll understand the danger and react appropriately.
- Try to stay upright and back out of the area the way you came, warn any other swimmers in the area of the danger, and then head for shore 100 yards or more from the dock.
- Alert the dock or marina owner and tell them to shut the power off to the dock until they locate the problem and correct it.
- Go to the hospital, explain what happened, and ask to be checked over to be sure there are no adverse health effects.
- Know how to distinguish drowning from ESD (drowning victims cannot speak and will appear to be trying to climb a ladder; tingling, numbness, or pain all indicate ESD).
- Fight the instinct to enter the water — many rescuers have died trying to help ESD victims.
- Call for help. Use 911 or VHF Channel 16 as appropriate.
- Turn off the shore power connection at the meter base and/or unplug shore power cords.
- Get the victim out of the water. Remember to reach, throw, row, but don't go.
- If the person is not breathing or you cannot get a pulse, perform CPR until the Fire Department, Coast Guard, or ambulance arrives.