Lightning?

[nagel]

Before I begin, No, I'm not saying to dive when it is lighting out.

Okay, on one of our dive trips it was raining for most of the day. Not a big deal. However, we got into this discussion about lightning. Obviously, we have always heard don't be in the water if it is lightning out. In fact, where we were diving they said they would shut down the diving if there was lightning within a mile of the area.

The discussion got into some theoretical talk about why. If lightning hit the water you will be electricuted - right? Why does it not fry the fish? Maybe if your in the water and touching ground would be the issue. Maybe the concern really is not with the water, but the fact that you are standing outdoors.

Did I sleep this day in 7th grade science class?

S. Nagel

 

[Midnight Star]

I'll dive when it's overcast, sunny, and raining ... but not when it's either lightning or looks like it's going to start. Electricity will only travel so far underwater due to "absorbtion" factors such as both organic and inorganic matter. How far it will travel, and at what voltage (starting vs. ending, with dissapation factored in) i'm not sure ... and i'm definatly not going to find out.

Good post BTW.

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Mike.

 

[Mark_J]

I'm not sure if you slept through Science class or not but lightning can kill fish and other marine life, the main factor is that they would need to be in close proximity to the strike. As lightning hits a body of water the voltage begins to immediately dissipate, although there are are some reports of people being hurt up to 30 yards away from a strike, that would not be common. Also, the deeper you are the less likely it is that you would be affected at all.

I still wouldn't dive in a lightning storm though, especially from a boat...

 

[Midnight Star]

Mark, did those reports of distance occur in salt or fresh water? I'm thinking that theoretically, a strike would go further in salt water due to the dissolved minerals, but not 100% sure. If it did go further, i'm guessing it probably wouldnt be by much.

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Mike.

 

[Mark_J]

That particular example was in salt water, it was on a beach if I recall correctly and was documented by the 45th Weather Squadron out of Florida...

I would agree with you in that salt water would conduct electricity more efficiently and that would raise the risk of a being affected by a strike

 

[Midnight Star]

I remember getting a "carpal" tunnel syndrome test, where they hooked up and "hit" my nerves of just my thumbs, with a good dose of electricity, just to measure my nerve response (watching the speed at which my thumb would contract). Man that seriously hurt!!! GRRRRrrr.... Could you imagine a jolt like that on every muscle of your body, all at once?

It would be interesting though to put voltage sensors at different horozontal distances under water, as well as straight down vertical depths, then use one of those "model rocket, wire totting, lightning rods" to direct the hit into water, just to see what the "area of impact" would be.

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Mike.

 

[lamont]

actually salt water should be safer since the salt water is a huge reservoir of charged particles and the lightning should conduct better in the salt water than through you (and lightning takes the path of least resistance), although steel tanks may be problematic -- particularly one the surface. in fresh water, its probably less likely to have a lightning strike on the water, but more likely that if it hits the water that it'll hit you since you'll conduct better than the surrounding water.

there's a story somewhere online of cave divers in a lightning storm that were getting zapped by lightning that went through the rock, through the water and through their bodies...

EDIT: here you go: http://www.scubaboard.com/showpost.php?p=199532&postcount=31

this thread also comes up often, a title search for lightning should turn up a lot of hits on previous threads...

(EDIT: check the rest of that thread: http://www.scubaboard.com/showthread.php?t=2150)

 

[Mark_J]

Lightning doesn't take the path of least resistance until after it already strikes something. Generally lightning strikes the highest point in an area, it doesn't measure conductivity before it strikes.

As for being safer in salt water, not necessarily true. The 45th Weather Squadron classifies water as the second most dangerous place to be in a lightning storm and doesn't differentiate between salt or fresh. In fact, the Gulf Stream is a lightning 'hot spot' and gets hit as often as the southern plains in the US.

 

[The Natural]

Lightining will only kill within a few feet of the strike to depth, also, it will bounce across the surface of the water, it doesn't penetrate to depth. So if you wind up diving when a storm comes through, stay below the surface until the last possible second, then get out of the water to limit your exposure.

Man I loved physics in HS.

 

[Lamnid]

I also thought that the metal tank wouldn't help but then you are coated ina generopus layer of rubber - aren't the rubber tyres on cars meant to prevent lighting? or was that something my parents made up to make me feel better about getting in the car? (come to think about it i haven't heard it anywhere else!)