Lightning is a massive and rapid discharge of static electricity that occurs when a significant electrical potential difference builds up within a storm cloud or between a cloud and the ground. Water bodies, such as lakes and oceans, often appear to be struck with unusual frequency. This observation leads to the common question of whether water attracts lightning. The scientific explanation, however, relates less to the water itself and more to the mechanics of the discharge process and the surrounding environment.
How Lightning Chooses Its Path
Lightning is a physical process dictated by the path of least electrical resistance; it does not choose a specific material to strike. The process begins with a negatively charged channel, known as the stepped leader, descending from the cloud base toward the ground. The stepped leader branches outward, testing various pathways by ionizing air molecules to create a conductive channel.
As the stepped leader nears the ground, its intense negative charge induces a strong positive charge on the ground and objects beneath it. This positive charge launches an upward streamer, a channel of ionized air that rises from the tallest or most pointed objects. The final path is determined when the stepped leader connects with an upward streamer, a process called attachment. The shortest distance between the cloud’s charge center and the ground is the most probable path because it minimizes the air resistance that must be overcome.
Height is the most influential factor in determining where attachment occurs. A taller object minimizes the distance the stepped leader must travel through non-ionized air. Since air is a poor conductor, any object that shortens the gap to the cloud base is electrically preferred. The visible lightning strike is the extremely bright return stroke that travels back up the established conductive channel at immense speed, carrying the bulk of the electrical current.
Why Large Bodies of Water Are Frequent Targets
Large bodies of water are frequently struck due to the physics of the shortest path in an open, flat environment. The water’s surface is a uniform plane, meaning there are no competing high points to launch upward streamers. In this unobstructed landscape, any object rising above the water instantly becomes the highest point in the immediate vicinity.
Objects like a person swimming, a fishing pole, or a sailboat mast provide the necessary height difference for an upward streamer to launch and connect with the stepped leader. These become isolated targets in an otherwise featureless electrical landscape. On land, the risk is dispersed by numerous alternative strike points like trees and buildings. On water, the highest point is often a temporary structure or a person, which makes the risk disproportionately high.
Water’s Electrical Properties Upon Impact
When lightning strikes water, the charge dispersion is dictated by the water’s electrical properties. Although pure water is a poor conductor, natural bodies of water contain dissolved salts, minerals, and impurities. These substances dissociate into ions, allowing the water to conduct the massive electrical current from the strike.
The electrical energy spreads outward rapidly from the contact point, primarily along the water’s surface rather than penetrating deeply. This radial dispersion creates a localized, high-voltage field that is extremely dangerous for anyone nearby. The difference in electrical potential between two points on the water’s surface, such as between a person’s feet, is known as step voltage. This voltage difference can drive a lethal current through the body even without a direct hit.
Essential Safety Guidelines
Anyone near or on the water during a thunderstorm must immediately seek a secure, enclosed shelter. Substantial buildings that contain plumbing and electrical wiring offer the best protection, as the current follows those conductive paths to the ground. An enclosed metal-topped vehicle with the windows closed also provides a safe alternative, acting like a Faraday cage to divert the current around the occupants.
Safety on the Water
If you are on a boat and cannot reach shore, move to an enclosed cabin and stay low, avoiding contact with metal objects or tall structures. If swimming or wading, get out of and away from the water immediately, as the current can spread many meters across the surface from the point of impact. Due to the risk of step voltage, minimize your contact with the ground or water. Do not lie flat on the ground or stand with your feet apart until the storm has safely passed.