Lightning striking a lake can kill a swimmer up to a hundred meters from the point of impact. The discharge itself lasts a fraction of a second, but the current spreads through water instantaneously. That's exactly why "just five more minutes" in the water as a storm approaches is a decision that can cost a life.

Water and electricity form one of the most dangerous combinations in nature. But most people picture the threat incorrectly: they imagine lightning has to strike them directly. In reality, a direct hit is rare. What kills is current spreading across the surface of a body of water for tens or hundreds of meters from the strike point.

What Happens in the Water When Lightning Strikes

A lightning discharge carries current up to 200,000 amperes at voltages of tens of millions of volts. When that energy hits water, it doesn't travel downward — it spreads across the surface layer in every direction from the point of contact.

Water is an efficient conductor, far better than air or dry ground. Current weakens with distance, but it does so slowly.

At 30 meters from the strike, voltage is still lethal. At 100 meters, it can trigger cardiac arrest. At 200 meters, seizures and loss of consciousness. For a swimmer, losing consciousness in water is equivalent to drowning.

The size of the body of water doesn't matter. A small pond, a river, a lake, a sea cove — if lightning strikes the water, current propagates through it the same way.

Why a Swimmer Is a Perfect Target

Three factors make a person in the water especially vulnerable.

1) The body is a conductor within a conductor.

On land, when lightning strikes ground nearby, current passes through the legs — a small area of contact. In water, the entire body is submerged in a conductive medium. Current passes through the chest, heart, brain — every vital organ lies in the discharge's path.

2) A person is the highest point.

On the flat surface of a body of water, a swimmer's head and shoulders protrude above the surface. Lightning strikes elevated points, and on open water, a person can become the discharge's point of attraction. This applies to those standing waist-deep, those swimming, and those sitting in a boat.

3) Escape becomes impossible.

Even if the current doesn't kill instantly, it triggers muscle seizures. A person whose muscles lock up in water drowns within seconds. On land, the same seizure means falling down. In water, it means death.

How Far From Water Is Actually Safe

There's no clear-cut threshold beyond which danger vanishes — too many variables are involved: discharge strength, water salinity, shoreline terrain. But practical guidance, based on data from meteorological services and rescue organizations, looks like this.

Get out of the water — the first and most important step. As long as you're in the water, you're within the strike zone, regardless of the storm's distance.

Move at least 100 meters from the water's edge. Wet sand, clay, and grass along the shore all conduct current. Lightning striking water near the bank can injure someone standing on wet sand just a few meters away. A hundred meters is the minimum safe distance from the edge of any body of water.

Don't shelter under trees near the shore. A lone tree on a lakeshore is one of the most dangerous spots during a storm. Lightning strikes the tree, current runs down the trunk and spreads through the wet ground — and if water is nearby, the strike zone expands.

Don't stay on an open shore. A flat shoreline with no shelter is a bad place to be. A person becomes the highest point on a level surface. It's safer to seek out terrain features — a ravine, a low spot, a ditch. Crouch down, hug your knees, and minimize contact with the ground.

Different Bodies of Water, Different Risk Levels

  • Open sea and large lakes

Maximum risk. A swimmer is the only elevated point on a vast conductive surface. A storm cell may be visible from far away, but there might not be time to reach shore. On large bodies of water, get out at the first signs of a storm — don't wait for rain.

  • Rivers

Slightly less dangerous than a lake — banks are higher, and trees along the edges intercept some discharges. But if lightning strikes the water, current spreads just the same. Wide sections with low banks are especially risky.

  • Outdoor swimming pools

No less dangerous than a lake. Water conducts, and metal handrails and ladders are additional conductors. During a storm, leave the pool immediately and move indoors.

  • Indoor pools

Safe — the building acts like a Faraday cage, channeling the discharge through the structure into the ground. But metal water pipes could theoretically conduct current, which is why some rescue services recommend stopping swimming even in indoor pools.

How to Tell a Storm Is Dangerously Close

A simple rule: count the seconds between the lightning flash and the thunderclap. Divide by three to get the distance in kilometers. Sound travels roughly 330 meters per second.

  • 30 seconds between flash and thunder — the storm is 10 kilometers away. Time to get out of the water.
  • 15 seconds — 5 kilometers. You should already be on shore and moving away from the water.
  • 6 seconds — 2 kilometers. Critically close. Seek shelter.
  • Flash and thunder simultaneously — the storm is directly overhead.

The "30/30 rule": leave the water if the gap between flash and thunder is under 30 seconds. Don't return for at least 30 minutes after the last clap — the storm can circle back.

If Someone Is Injured

A person struck by lightning can and should be touched — there's no residual charge in their body, and they pose no danger. First: call emergency services at 112. Second: check breathing and pulse.

If breathing has stopped, begin CPR: 30 chest compressions, 2 rescue breaths, continuing without pause until medical personnel arrive.

For a lightning-related electrical injury, CPR is often the only thing that can save a life. The brain survives without oxygen for 4–6 minutes — every second counts.

Move the injured person at least 50 meters from the strike site — a repeat discharge to the same spot is possible.

One Number Worth Remembering

One hundred meters. That's the minimum distance from any body of water you should maintain during a thunderstorm. Closer, and you're in the danger zone. Farther, and you're significantly safer. Best of all is being inside a building or a car with the windows closed: the metal frame channels the discharge into the ground without touching you.

A thunderstorm lasts an average of 30–40 minutes. That half hour of patience is worth it to avoid becoming part of a statistic in which every case is someone's life.