Protect against lightning strikes on the water

Lighting strikes nearly one out of 1,000 boats every year. Most strikes occur between noon and 6 p.m. If you’re out on the water when a thunderstorm rolls in, take immediate action to protect yourself and your boat from lightning strikes.

Step 1: Recognize dangerous conditions

As the air temperature warms, evaporation increases. This warm, moisture-laden air rises and evaporates, forming fluffy cumulus clouds. As moisture accumulates, the clouds darken and become cumulonimbus, or thunderstorm, clouds.

Well-developed thunderstorm clouds have flat anvil-shaped tops. These clouds can reach 40,000 feet or more. The cloud’s upper portion develops a positive electrical charge. And the cloud’s lower portion develops a negative electrical charge. Lightning occurs when the difference between these charges—the electrical potential—becomes large enough to overcome the insulating air’s resistance and force a conductive path between the two charges. This electrical potential could reach 100 million volts.

In most cases, lightning strikes represent current flowing from negative to positive. In other words, the current moves from the bottom to the top of a cloud, from cloud to cloud, or (most feared) from cloud to ground.

Lightning most often strikes the highest object in the immediate area. On a body of water, that object is your boat. In a small open boat, that object is you.

Step 2: Take immediate action

When a thunderstorm catches you on the water, take action immediately.

Stay in the center of the cabin if your boat has one. If not, stay as low in the boat as possible.
Keep arms and legs in the boat. Don’t dangle them in the water.
Stop all water activities—fishing, skiing, scuba diving and swimming—when weather conditions look threatening or you see lightning. Furthermore, lightning can strike a mile or more in front of approaching thunderstorm clouds.
Disconnect and don’t touch electronic equipment, including the radio, during the storm. Lower, remove, or tie down the radio antenna and other protruding devices that aren’t part of the lightning protection system.
Avoid touching any portion of the boat that’s connected to the lightning protection system. In other words, never touch two components connected to the system at the same time.

If lightning strikes your boat or you suspect it has, check the electrical system and compasses for damage. –John Schwab

This article first appeared in Scuttlebutt, the newsletter of North Strand Sail & Power Squadron/26.