By Terry Johnson , University of Alaska Sea Grant, Marine Advisory Program

We all live safely with alternating current (AC) electricity in the home. But with the same voltage, the marine AC system is potentially more dangerous because the boat and the people who work on it are surrounded by water.

A person who becomes part of the pathway between a hot wire and the sea can experience severe shock. Forget the blinding flash and the smoking flesh. It doesn’t take a lot of juice to kill a person. Remember, what makes the heart tick is a faint electrical impulse generated within the muscle itself. It takes only a very small amount of current through the chest to disrupt the heart rhythm, causing fatal fluttering of the heart muscle called fibrillation.

A critical factor is where the current passes through the body. Touching hot and neutral leads with one hand can give you a jolt and maybe even a burn, but won’t kill you. But grabbing a hot lead with one hand and a neutral with the other, or the lead with one hand while standing in water, can send the current through the chest.

One effect that electrical current has on the body is to make muscles contract, so a person getting a shock may be unable to release the item that’s carrying the current. The body isn’t a perfect conductor of electricity, but passing through the chest it takes only 0.05 amp to kill. That’s barely enough to light a small bulb, and an amount which easily can pass through a human body that becomes a conduit between a hot AC wire and ground.

No one intentionally grabs a hot wire, but things happen. Two-prong plugs get put into sockets backwards (a condition known as reverse polarity). Circuitry chafes or cracks, exposing bare wire. Wiring inside a power tool breaks and contacts the metal case. Pick up with one hand an electric drill that has a loose wire inside, while bracing against the engine block with the other hand, and you could be the next industrial fatality.