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Does anyone know whether a lightning strike in water would induce a shock
wave? It seems to me that a greater danger would be from that as opposed
to the electircal dischage.


> It is my understanding that lightning originates from the ground and goes 
> up not the reverse.
> 
> On Wed, 12 Jul 1995 UnderhillP@ao*.co* wrote:
> 
> > 
> > >Now, knowing weather in colorado like I do, it rains, almost always with
> > lightning in the early 
> > >afternoons.
> > >
> > >Suppose that somehow, my decompression time happens to come about the same
> > time as an afternoon
> > >lightning storm? Does being in a moderate sized body of water (say 100
> > meters across) constitute a 
> > >major hazard? (Seems like a silly question at first, but people in the
> > ocean during storms dont seem 
> > >to die too often.) (do they?)
> > 
> > Lightning always takes the easiest path to ground.  That seems pretty
> > straightforward but the story doesn't end there.  Once a lightning strike
> > hits, the charge has to dissipate into the surrounding ground (or water).
> > 
> > In a large body of salt water, which is a good conductor, the charge will
> > rapidly dissipate in a uniform manner.  Very fresh water is a very poor
> > conductor of electricity and the charge will follow the easiest path.  A
> > human body contains a lot of salt water and is therefore a much better
> > conductor than fresh water.  Guess what?  Some of the energy from a nearby
> > strike will "channel" through you, the hapless diver.  Fortunately your
tanks
> > are a much better conductor than you are and will carry some of the current
> > away from your torso.  Rocks also have varying conductivities.  Limestone
> > tends to have poor conductivity which is part of the reason why lightning
has
> > been known to strike deep into air filled caves (killing people sheltering
> > there!) because the damp air in the cave was a better conductor than the
> > surrounding rock.
> > 
> > The tiniest amount of dissolved minerals will dramatically affect the
> > conductivity of fresh water, similarly, the moisture and mineral content of
> > surrounding soils and rock will dramatically affect its conductivity.
> >  Therefore, it is difficult to say whether the rock or water will conduct
> > best and therefore where the "easiest path" will be.
> > 
> > There are other factors involved, such as charge density.  Lightning prefers
> > to hit pointed objects which stick up from their surroundings (trees,
fences,
> > poles, etc.)  A diver, submerged in the water is not sticking up at all, but
> > a diver on the surface, in the middle of a big lake could be an animated
> > lightning attractor.
> > 
> > >So long as you are in the open water, and not grounded to one of the water
> > >edges or any of the mine debris, you should be in relative safety. I have
> > >heard of a diver or two being in the water in the very close proximity of a
> > >strike, the report was that it was an "energizing" experiance, but they
came
> > >away none the worse for wear.
> > 
> > I don't think it would matter if you were in contact with the water edges
but
> > if you were touching or near to any metallic junk (quite likely in a mine,
> > I'm sure) then you could be in trouble were there to be a nearby strike.
> > 

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