While a direct hit on an individual fish is extremely rare, lightning’s interaction with water is a complex phenomenon that can affect creatures beneath the surface. Understanding how electricity behaves in water helps clarify the risks for marine life and humans during a thunderstorm.
Lightning’s Interaction with Water
When lightning strikes a body of water, its electrical charge spreads rapidly. Water, particularly saltwater, acts as a conductor. This rapid dispersion happens because water contains dissolved minerals and salts, which provide ions that facilitate the flow of electrical current. The energy from a lightning strike typically spreads outward and downward in a hemispherical pattern from the point of impact.
The electrical current from a lightning strike primarily travels across the surface of the water, and its intensity decreases significantly with both distance and depth. For instance, the lethal current is believed to spread horizontally up to about 20 feet from the strike point on the surface. Vertically, the current fully dissipates less than 10 feet below the surface in saltwater. This quick dissipation means that while the initial impact zone is dangerous, the electrical charge weakens rapidly away from it.
Freshwater, compared to saltwater, is a poorer conductor of electricity. This difference in conductivity means that when lightning strikes freshwater, the electrical current may not disperse as widely or quickly, potentially concentrating the charge more intensely in a smaller area. Conversely, the high salt content in seawater allows the current to pervade more widely and quickly, reducing the localized intensity.
Effects on Fish and Other Aquatic Creatures
A direct strike on an individual fish is highly improbable, as most fish remain submerged rather than at the surface. However, fish near the surface or in the immediate vicinity of a strike can be affected. The rapid spread of electricity through the water creates an electrical field that can stun or kill fish within a few meters of the strike area. This electrical surge can interfere with a fish’s natural electrical signals, potentially causing its heart to stop or fibrillate, leading to death.
Factors such as the fish’s distance from the strike, the depth of the water, and the overall size of the body of water influence the severity of the effect. Fish located deeper than a few meters (6 to 10 feet) are unaffected because the electrical current dissipates quickly with depth. In large bodies of water like oceans, the vastness reduces the likelihood of a fish being in a dangerous electrical field. While individual fish near the surface might perish, mass die-offs of fish due to lightning strikes are not common.
Beyond the electrical shock, the immense energy released by a lightning strike can also generate an explosive sound wave pressure, which might contribute to the death of aquatic animals in the vicinity. However, the primary mechanism of harm is the electrical current itself. Fish are safer during a thunderstorm than humans on or near the water, as they are deeper in the water column where the current is less concentrated.
Human Safety Around Water During Storms
The principles of how lightning behaves in water have direct implications for human safety. Being in or near water during a thunderstorm presents a significant danger because the human body is a good conductor of electricity. When lightning strikes water, the electrical current spreads out, and anyone in its path can be electrocuted. The risk is particularly high for individuals swimming or engaging in water sports, as they are often at or near the surface where the electrical discharge is most concentrated.
Seek immediate shelter if thunder is heard or lightning is seen, as lightning can strike many miles from a storm’s center. Safe locations include enclosed buildings with wiring and plumbing, or hard-topped metal vehicles with closed windows. Open structures like gazebos, tents, or covered porches do not offer adequate protection. Also, avoid contact with plumbing and running water inside a building during a thunderstorm, as lightning can travel through metal pipes. Stay out of and away from all bodies of water for at least 30 minutes after the last rumble of thunder.