Does Lightning Ever Kill Fish in the Ocean?

Lightning strikes on the ocean are relatively uncommon compared to strikes on land. However, when lightning does strike the sea, it can potentially kill fish near the surface. The electrical charge from a lightning bolt spreads out sideways and downwards in an expanding half-sphere from the point of impact. Fish within a few meters of the strike area would likely be killed, but beyond that, they would probably just feel a slight tingle.
Why Don’t Most Fish Die When Lightning Strikes the Ocean?
Most fish are able to survive lightning strikes because they typically swim at depths below the surface where the electrical current is concentrated. The further away a fish is from the strike, the lower the change in voltage per unit of distance, similar to how the pressure difference decreases with distance from an explosion.
Additionally, saltwater is an excellent conductor, so when lightning strikes the ocean surface, the current is primarily spread across the surface of the conductor, almost like a protective shell
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. This phenomenon is known as the skin effect
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Dangers to Marine Mammals and Scuba Divers
While fish are generally safe from lightning strikes due to their depth in the water, animals at the surface like whales and dolphins are more vulnerable. Biologists agree that it is entirely possible for marine mammals to be killed by lightning, but there is limited direct evidence of this happening in the past.

Scuba Divers

Scuba divers are also at risk when lightning strikes the ocean. Several divers have been killed by lightning in the past, often as they surface during a thunderstorm. The diving tanks act as giant conductors, making divers a prime target for lightning strikes. It is highly recommended to avoid diving during lightning storms.
How Many Fish Are in the Ocean?
There are approximately 3.5 trillion fish in the Atlantic Ocean alone
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. With such a vast population, only a small fraction of fish would be affected by a lightning strike at any given time
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. While a handful of fish may suffer electrical and heat damage from lightning, it is not enough to significantly impact the overall fish population
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Conclusion
In summary, while lightning can kill fish that are near the surface when a strike occurs, most fish are able to survive due to their depth in the water and the way electricity behaves in saltwater. However, marine mammals and scuba divers are at greater risk and should avoid being in the water during thunderstorms. The vast population of fish in the ocean ensures that only a tiny fraction would be affected by lightning strikes, which are relatively uncommon in the first place.