I wrote a draft of this post last week, and wanted Kevin Ritz, President of the Electric Shock Drowning Prevention Association, to check its accuracy before going to press. In the interim three more children have died from Electric Shock Drowning (ESD).
I first became aware of ESD when I showed up for my first day at Kevin's ABYC Marine Electrical Certification course. After the first hour of class Kevin had us riveted, when we were all expecting a fairly dull week of electrical standards study. Kevin has dedicated his life to marine electrical safety because in 1999 his eight-year-old son Lucas died from ESD while swimming near their marina in Oregon. Kevin is a man on a mission and he tasked us with preventing ESD deaths in the future.
Kevin’s challenge has been not only to improve safety, but to make the world understand this invisible killer. Often misidentified as simple drowning, ESD leaves no trace: it simply stops the heart and paralyzes the lungs. Sometimes, as with Kevin’s son, the victim’s head never even goes underwater. In ESD the heart’s electrical signals are disrupted so badly that the victim often can’t be revived, even using a defibrillator.
When a strong swimmer who hasn’t been drinking suddenly drowns near a fresh water marina, ESD should always be suspected. It is coming to light that ESD is the cause of death in many more of these incidents than previously imagined.
Most victims are young, because young people are more likely to be frolicking in the water. And often the first victim is followed by a second, who jumps in the water to help someone who appears to be drowning.
At least fifty people have died in the US from ESD since the mid-eighties, when people like Kevin first started putting two and two together. This list in inconclusive, and the number is probably much higher, because implicating ESD is circumstantial.
Sea water is 300 times more conductive than fresh water. You’d think this would make sea water more dangerous, but just the opposite: Our bodies are saline--about the same conductivity as sea water--so in sea water we’re nothing special. In fresh water, however, we are a little floating island of good conductivity in a sea of poor conductivity. Stray current tries to get back to its source by the path of least resistance, so it will “jump” through a saline human who swims in fresh water. It only takes a small voltage gradient in the water (as little as 2 volts per foot) to cause cardiac and respiratory paralysis.
Sometimes a marina’s wiring is implicated, but more often the culprit is inadequate grounding or bonding aboard a boat combined with an errant AC connection to the surrounding water, usually via the propeller shaft or a thru-hull.
A solution? The ELCI, mentioned in a previous blog post, would have prevented almost all of these ESD accidents. New to the standard in the US, I’ve installed several ELCIs this year, and I'm recommending them to everyone.
If you are swimming and feel a tingling sensation or muscle paralysis, back up! The voltage gradient radiates from the current leak and increases as you get closer. Also, stay upright. Upright, in a treading water position, you cover only a few feet of voltage gradient, but by swimming horizontally you could worsen the situation by covering voltage gradients with the entire length of your body.
As electricians we have to be careful what we say, because any kind of electricity can be dangerous, but AC is the culprit in most marine electrical accidents, and AC systems are where most confusion lies. Marine AC wiring is NOT the same as shore-based AC wiring, and a land-trained electrician can make some terrible mistakes on a boat. If you’re not completely sure what you’re doing with AC, hire a professional. Most marine electricians can carry out a fairly thorough AC safety survey in less than an hour, which doesn’t cost much, and most are happy to do this as a “public service.”