# The Naked Scientists Forum

### Author Topic: What happens when lightning hits the surface of the sea?  (Read 26542 times)

#### paul.fr

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##### What happens when lightning hits the surface of the sea?
« on: 24/04/2007 07:20:11 »
When lightening hits the sea do fish get shocked? Also, say you were scubadiving and lightening hit the sae. would you get a bigger shock than you would on land?
« Last Edit: 03/05/2007 08:24:37 by chris »

#### Karen W.

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##### Re: What happens when lightning hits the surface of the sea?
« Reply #1 on: 24/04/2007 07:29:13 »
Wow Those are great questions, will salt do anything to stop the shock.. I am just trying to see the differences in water. Surely the shock would kill fish unless salt or something else acted as a shield or perhaps it only travels so far in water ,,,hmmmm very good question and I don't know.. LOL i do however want to know you have made me curious!

#### lightarrow

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##### Re: What happens when lightning hits the surface of the sea?
« Reply #2 on: 24/04/2007 16:23:45 »
When lightening hits the sea do fish get shocked?
You want roasted fish without even fish it? Lazy man!
Quote
Also, say you were scubadiving and lightening hit the sae. would you get a bigger shock than you would on land?

I would say a less shock, if the total lightening current is the same(*), for 2 reasons:
1. you are covered with salted water, which is conductive, so the fraction of the current going through your body should be less than 100%.
2. you lay horizontally, so the section of your body through which the current goes is larger, so the current density is smaller.

(*)Of course it depends on the assumption that the current is the same as that of a lightning hitting you while standing up on land. This assumption depends on the lightning "proper" strenght, that is on the potensial difference ΔV, and on the electrical resistance it founds on its path (which is less if you lay horizontally...)

#### Ben6789

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##### Re: What happens when lightning hits the surface of the sea?
« Reply #3 on: 24/04/2007 16:31:30 »
I think Karen makes a good point, would the salt dampen it?

#### tony6789

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##### Re: What happens when lightning hits the surface of the sea?
« Reply #4 on: 24/04/2007 16:32:25 »
im thinking that it depens on how deep the fish or u are if u are close then the salt doesnt haveenuf time to abosorb where as if u r farther down then the shock is abosorbed in the salt so basically it just depends on the deepness that u are in the water

#### Ben6789

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##### Re: What happens when lightning hits the surface of the sea?
« Reply #5 on: 24/04/2007 16:33:25 »
What if there's no salt? Would the electricity go on forever until it hit you?

#### ukmicky

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##### Re: What happens when lightning hits the surface of the sea?
« Reply #6 on: 24/04/2007 17:17:18 »
I heard the second most dangerous place to be during a thunderstorm is in open water however i have also heard that lightning vary rarely strikes the sea and strikes at sea usally involve a ship of some sort.

#### DrDick

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##### Re: What happens when lightning hits the surface of the sea?
« Reply #7 on: 24/04/2007 17:20:20 »
The salt in the water is what allows the water to conduct electricity in the first place.  Pure water is a terrible conductor of electricity.  (Most water is not pure, however.)

Most likely (I'm kind of guessing here), any fish very close to the lightning strike would die.  A little ways away from the strike, however, they should be fine, since the electricity would probably be conducted around them (the conductivity of the water is greater than the conductivity of the fish themselves).

The situation should be similar to a bird on a power line.  The electricity would rather go through the wire than through the bird, UNLESS the bird touches the ground line.  In that case, the electricity has an easier path to ground than going straight ahead.

In the water, it's like being immersed in the wire.  The current should flow around you.

In the near vicinity of the strike, however, the shock wave alone might be enough to kill.

Dick

#### DrDick

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##### Re: What happens when lightning hits the surface of the sea?
« Reply #8 on: 24/04/2007 17:21:25 »
I heard the second most dangerous place to be during a thunderstorm is in open water however i have also heard that lightning vary rarely strikes the sea and strikes at sea usally involve a ship of some sort.

Yes, because you're not actually IN the water.  You're above the water, providing a pathway for the charge to travel.

Dick

#### lyner

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##### Re: What happens when lightning hits the surface of the sea?
« Reply #9 on: 27/04/2007 19:57:26 »
The main factor in getting a shock is the number of volts per metre (or Electric Field). There may be many thousands of Amps of current flowing into the seawater where the lightning strikes. This current flowing through the  (albeit, pretty low) resistance of the seawater will be enough to produce a significantly 'shocking' field close to the strike  if you were swimming.  BUT, the current spreads out over a hemisphere and the 'current density' rapidly decreases (the inverse square law) as you get further away.
By the time you are a few tens of  metres away from the strike, the effective field will reduce significantly. It would be real 'sods law' if you found yourself  swimming right next to the strike point. The local fish would be sure to suffer, though.
The body's resistance is much the same as that of seawater and there would be a good contact, of course.
The actual effect of electric shock depends on total charge passing through you and what actual path it takes (e.g. across the heart or just between two fingers).
Although a lightning strike carries a huge current, it is very brief , so the actual charge and biological damage may not be as bad as you'd think.
Has anyone had experience of this?

#### iko

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##### What happens when lightning hits the surface of the sea?
« Reply #10 on: 13/07/2007 17:11:19 »

Lightning at Sea

...
- Don't be a target!

Over 10% of deaths on cruising sailing boats alone at sea are caused by lightning. This is a tragedy to those families affected but one that we can take precautions to protect ourselves against...

Standing out as they do above the vast expanse of ocean water, marine vessels can be a prime target for a lightning leader seeking the most attractive path to ground - especially those with masts! Moreover, if the vessel does not have a metal hull and is not earthed to the water, the danger is multiplied considerably.

Often the most at risk are small boats, as these are more frequently constructed of wood or fibreglass, which are poor conductors of electricity, rather than metal - compared to the human body, which is an excellent conductor! Sailing vessels with portable masts, or vessels with the mast mounted on the cabin roof are particularly vulnerable as they are usually the least protected as far as grounding or bonding is concerned.

As incidence of lightning varies throughout the world, so logic dictates will the risk. However, while you may live in a region where lightning is relatively scarce, your sailing career may take you into areas of much higher risk. It is not unusual for the novice inshore sailor to become far more ambitious once the sailing bug takes hold
...

#### chris

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##### What happens when lightning hits the surface of the sea?
« Reply #11 on: 11/07/2008 09:39:34 »
Am I at higher risk from lightning strike electrocution if I am swimming in a fresh water lake or pond than the sea, given that salt water is so much more conductive?

Chris

#### einsteinium252

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##### What happens when lightning hits the surface of the sea?
« Reply #12 on: 25/07/2008 07:26:06 »
Pure water is a terrible conductor of electricity.  (Most water is not pure, however.)

Chris,

As DrDick has stated, most ponds or lakes have certain ammounts of mineral deposits that can make the pure water conductive.  When lighting discharges into any ground, it dissipates outward.  If a human, or fish, heart were to be near the lightning strike there would be a higher voltage on one side of the heart, which would cause the electricity to pass through the heart and cause cardial arrest (at high enough voltage and current).

Since our bodies are largely salt water, we would be the path of least resistance in fresh water and the path of most resistance in salt water.

#### graham.d

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##### What happens when lightning hits the surface of the sea?
« Reply #13 on: 25/07/2008 09:33:48 »
It always bothers me if there is a thunderstorm whilst out sailing. There is this large metal mast sticking up which is conveniently (as far as the lightning is concerned) connected to the boat's "earth", which is contact with the sea. You don't hear of such things very often though.

#### The Naked Scientists Forum

##### What happens when lightning hits the surface of the sea?
« Reply #13 on: 25/07/2008 09:33:48 »