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What to do when you see lightning while swimming

Ever wondered when you should exit the water while swimming as a thunderstorm approaches? Here we discuss why swimming in a storm isn’t safe and when to exit the water.

Storms are inevitable on the coast and with the storm season rapidly approaching, we’re already seeing major thunderstorm activity around the country.

In this article, we look at why swimming in a lightning storm is not safe and how to assess the risk as a storm is approaching.

Is it safe to swim during a lightning storm? 

The short answer is, no.

Swimming in a thunderstorm with lightning present is not safe, whether you’re in the ocean or a pool.

A body of water is the equivalent of putting a hairdryer in a bath, and because water conducts electricity, lightning is more likely to strike water than land.

If the water you’re swimming in gets struck by lightning it can severely injure you or even kill you.

What happens when lightning strikes water?

When lightning strikes water the electric charge doesn’t penetrate deep into the water, but rather, it spreads across the surface, dispersing horizontally.

This electric charge can travel as little as 10m or as much as 100m or more, depending on the power of the lightning bolt itself.

From a swimmers point of view, this means the bolt of lightning doesn’t have to hit you directly for it to cause harm.

The 30-30 rule for determining whether to exit the water

Staying safe while swimming as a storm is approaching is extremely important.

Royal Life Saving recommends using the 30-30 rule if swimming when a storm is approaching to determine when you should exit the water.

What’s the 30-30 rule?

This is when you start counting to 30 when you see a flash of lightning.

If you hear thunder at or before 30 seconds, then the thunderstorm is close enough for lightning to strike the water around you and therefore it is deemed too dangerous to be swimming in water.

The closer to zero you hear thunder after a lightning strike the closer the storm is to you.

Royal Life Saving also recommends waiting at least 30 minutes after the last visible lightning strike before entering the water again to ensure the storm and lightning has fully cleared the area.

Further advice for ocean swimmers

Andre Slade from OceanFit goes a step further with his advice for ocean swimmers.

“The main difference between the 30-30 rule for pool swimming and ocean swimming is the speed at which you can exit the water and get undercover and away from the potential harm of a lightning strike,” says Slade.

“If you’re out the back and a storm is approaching, it could take some time to get back to the beach, and up to safety, so swimmers need to factor this into the 30-30 rule.

“Perhaps ocean swimmers could double it, call it the 30-60 rule.

“Ultimately, if you are in any doubt, you should just get out of the ocean as soon as possible.”

Whilst the rule for exiting the water is a good way to approach thunderstorms, Slade suggests thinking further ahead.

“Before you go for an ocean swim, check the weather forecast. The BOM will put out localised warnings for thunderstorms so check that, and if there’s a storm due when you’re thinking of going for a swim, sit it out or wait until the storm has obviously cleared.”

Thunderstorms can be dangerous especially when swimming. It is important to always take the necessary precautions to keep yourself and others safe when swimming as thunderstorms approach.

  • Written by Ocean Swims on 29 October 2021
  • (Updated on 3 August 2023)



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