Danger at the Dock
How many times have you let your kids go for a swim off a dock at the lake? Seems harmless enough, particularly if they are wearing a life jacket. But in recent years, there have been more and more reports of people being electrocuted while swimming in a body of fresh water, such as a lake. This is a phenomenon called electric shock drowning (ESD) and can cause a fun day on the water to go horribly wrong.
Why Does it Happen?
ESD occurs when electricity from a boat or a dock "leaks" into the water around it. A person in the electrified water can experience anything from a mild tingling to a shock that passes through the body with enough force to cause muscular paralysis, causing the person to drown. It typically occurs in fresh water rather than sea water because sea water conducts electricity better than fresh water. (Electrical current looks for something to flow through. In salt water, it can flow through the salt. In fresh water, there is nothing. However, it can pass through a human body that's in the water. If there's enough current passing through the body, things can go horribly wrong in a hurry. In salt water, the current flows around you, not through you.)
According to Boating1 magazine, at least eight deaths were attributed to faulty boat and dockside wiring in 2012. Many more fatalities listed as drowning were likely caused by ESD. In the past, it's been difficult to determine exactly how many drownings have occurred due to electric shock because an autopsy won't reveal signs of ESD.
Prevention for Swimmers
There's no way to tell if the water you're getting ready to jump into is electrified just by looking at it, and most people don't know they should check it or even how to check it. The best thing you can do to keep yourself safe is to stay out of the water around a dock or marina that may be electrified. If you are already in the water and feel a tingling sensation, resist the urge to swim towards the dock. Instead, head for a shoreline at least 100 yards from the dock and yell for others not to go in the water. If you see someone in the water who needs help, follow the U.S. Army's advice: reach, throw, row—but don't go.2
Prevention for Boat and Dock Owners
If you own a boat, have it checked at least once a year by an electrician who is familiar with the safety standards of the American Boat and Yacht Council (ABYC) to make sure no electricity is leaking. You may also have them install an equipment leakage circuit interrupter (ELCI) on your boat or on the shore power cord, or use a ground fault circuit interrupter (GFCI) in the shore power cord. Have the electrician explain how to use this equipment, and make sure you test it every time you take your boat out.
If you own a dock or a marina that is electrified, do not allow swimming within 100 yards. In addition, have your dock checked periodically to ensure there are no safety issues.
One of the most important things you can do is to educate yourself and others about ESD, especially children. Make sure they know why they shouldn't just jump right in the water. Doing so may save lives!
1 - http://www.boatingmag.com/how-to/electric-shock-drowning-prevention2 - http://www.army.mil/article/51402/