Go into any marina and you will probably see a sign indicating that swimming is not allowed in the marina. It would be natural to assume that this is because of the danger of a swimmer being in the water while boat traffic is present. That is correct but there is another reason: electric shock drowning (ESD). While the numbers are hard to quantify, it has been reported that many people are killed each year because of ESD. We just had one such drowning on Lake Lanier last July.
So how does this happen? ESD usually occurs when a person is swimming near a dock or a boat. An electrical fault in the 120 volt electrical system on the dock or boat causes an electrical current to be introduced into the water and it electrocutes the swimmer. This electrical current can come from the shore power feed on the dock or from a boat’s generator if it is running. It is very similar to turning on a hair dryer and tossing it into a bathtub. Note that ESD typically occurs in fresh water because of its lack of conductivity but it can also occur in salt water.
A swimmer who is affected by an electrical current can experience paralysis and even stoppage of the heart rendering the victim totally helpless. Rescuing a person who has been affected can be very difficult, because a rescuer could also be overcome by the electrical current.
So how can you prevent ESD? The first thing to remember is that it is not a good idea to swim around a dock where there are boats connected to shore power. All it takes is for a boat or the power pedestal on the dock to experience a ground fault issue and you will have a dangerous situation. If you are a boat owner and your vessel is experiencing an electrical issue, have it checked out by a licensed marine electrician immediately. The same applies if the shore power on your dock is having issues.
Here are some additional things to keep in mind about ESD:
- There is no way to tell if there is a current in the water by looking at it.
- A swimmer can enter the water and not feel a current immediately because the issue can be intermittent. The water may be fine one minute and dangerous the next.
- You may be diligent about the maintenance of your vessel and your dock’s electrical systems but you do not know the maintenance history of other vessels and docks.
- Although you may wear a life jacket, exposure to a strong electrical current could still result in cardiac arrest.
- The number of people killed by ESD each year is difficult to determine because the incident does not leave evidence. Oftentimes it is assumed that individuals who succumbed to ESD simply drowned.
It is better to be safe than sorry. Before you jump into the water from a dock, think twice. It could literally save your life.