Will Lightning Kill You While Scuba Diving?

We have all been there, you are gearing up for a dive and suddenly the sky lights up in thunder. The dive is cancelled because a lightning strike can kill you when you’re in the water when it strikes, right? Well, will lightning kill you while scuba diving?

So, will lightning kill you when you’re scuba diving? In every open water book you’ll ever read the first thing you’ll read about weather is: Get out the water as soon as you see lightning! But how dangerous is this really? I don’t see any fish floating belly up after a big thunderstorm. And what to do when you’re already diving and it’s starts? With 12 percent of lightning fatalities in the US near or on the water. Lightning is one of the most dangerous weather phenomenons divers will face.

The science

First of all lightning will rarely strike in an ocean. Oceans normally don’t heat up enough to become positively charged for lightning to occur and thus don’t attract lightning. Also, water is almost always the lowest part compared to surrounding land which is also warmer and therefore more positively charged. That being said, water is a great conductor and will carry a long way through water. Making it a big risk for anyone or anything in the water.

There is one upside to this charatastic and that’s that because of the conductivity of water the strike will not penetrate to great depths. This means that the power of the strike will get weak quite fast. This is also the reason why you almost never see dead fish on the surface after a thunderstorm, even when lightning did strike the water. So as long as you stay below the surface on a considarble depth you would in theory be fine. The real danger however starts once you surface.

Just like everyone you eventually need to surface after a dive and that’s were the whole situation changes. As you clime onto the boat you and everybody in it suddenly become the highest point for miles. To make matters even worse everybody in the boat and the boat itself has a positive charge making a strike even more likely.

You are diving and you see lightning, what now?

Imagine you are diving and suddenly the underwater landscape lights up around you. A storm is raging above and you are not quite sure what to do. The thing you should do depends on the situation. If you are boat diving and there is someone on the boat waiting for you it’s best to end the dive. Head for the surface and get on the boat because the longer you stay down the more danger you put everyone in who’s already on the boat. Get to the middle of it and as low as possible without touching anything metal. Don’t sit on top of the boat to watch the light show either.

If the boat is empty or you are doing a shore dive the situation is different. As long as you’re at depth you are relatively safe and you could choose to wait it out. But there is a big fat but to this method. At one point you need to surface and if you choose to wait it out you might need to surface at the peak of the storm. This would mean putting yourself at greater risk by trying to wait for the storm to pass. Therefore my plan of action is to try to exit the water as soon as I get any notion of thunder or lightning. Hopefully being out of the water before the worse part of the storm hits.

To dive or not to dive?

When you are still on shore and a thunder storm is brewing the best thing to do is stay out of the water until it blows over. This may mean that you have to abort the dive as a whole. If you are already on the water and you can hear the thunder it’s time to head for shore because it means you are already at risk of being struck. The flash-to-bang method is a good way to determine if the lightning is close. Sound travels about one mile every five seconds. This can help you determine if the storm is getting closer.

The advice regarding to diving in thunderstorms is quite simple. Don’t be near or on the water 30 minutes before or after a thunderstorm. Just head inside and grab a drink and wait it out.

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