Lightning strikes and diving

[WeRtheOcean]

Saltwater acts like a Farraday cage.

But the OP said sweet water.

 

[GDHLEWIS]

If your in a tank with sweet water in it, chance are the tank its self would be earthed. Providing the tank is large enough you wouldn't feel anything providing you were far enough away from the strike. Would depend on distance from the strike...either way probably not best to dive in a storm if it can be avoided. Wet person carrying metal would be a bit of a target for lighting strikes whilst getting out of the water. You able to explain more on the situation if your in a tank? If so the size etc... Interesting topic

 

[Scubagolf]

The safest thing is to just carry a 2 iron with you

“Even God can’t hit a 1-iron.” Lee Trevino.

 

[Subcooled]

Saltwater acts like a Farraday cage. Electricity generally spreads along the surface as the path of least resistance

Thanks.

1. Charge

• When I think about it, there's a build-up of charge (in a certain region of course; electrons are not born neither do they die, they just move around) prior to the lightning bolt. The exact nature of the "charge" is complicated of course. Electrons are usually not completely free but part of (other) matter.
• Obviously, charge is drawn towards the clouds, hence it's on the surface. Or, near the surface, as these electrons (etc) each want a space of their own. Electrons may be dimensionless but charge does take volume.
• When the voltage between cloud and water grows too great for air to insulate it, a lightning bolt happens. Electrons move.
• It is only natural then that the current once it hits water would mainly dissipate horizontally - along the path of least resistance as you say.
• I fear though, that the reality is a little more messy, and the currents might actually travel a bit down, especially in sweet water. Extreme currents and plasma are involved after all. If anecdotal evidence (15-20ft might be safe) is the best knowledge we have, then at least we have something.
• When I see how current channels through air (an insulator) I would add some depth in sweet water.
• I guess we can agree on one thing: to resurface during a thunderstorm is dangerous.

2. Pressure

• When 50 000 F plasma comes into contact with water, the water surely warms up a bit. A lightning lasts for a very short moment though.
• This video, where a lightning strikes a spring causing panic in divers, who then the flee for higher ground and metal objects (ouch!), hints that a lightning bolt is not quite a depth charge. Probably safest to stay submerged.

 

[Gene]

Most north Florida springs and cave divers have been in and around water during a thunderstorm. We were snorkeling down the Ichetucknee one time and a strong summer afternoon thunderstorm popped up for about 30 minutes. We just kept going, thinking the tall trees along the bank would take the hit.
Another time I heard thunder while on deco at Ginnie and surfaced to a full blown thunderstorm with lightning hitting too close for comfort. I stayed in the water for about five minutes or so before making the decision to get to my near-by parked car and just dump my doubles and gear into the back of my Land Rover while rain poured in. I went to a closed bank drive-thru in High Springs to sort the gear out.
Someone else can give more details about this story as it didn't happen to me, but some divers were swimming in the cave at Peacock Springs one time and felt a buzzing in their teeth. Turns out they were swimming beneath a large tree above them that was struck. Not sure what their depth was but probably 60 feet or so.
Lastly, I remember reading a news story about a person struck by lightning on a beach in South Florida and he died. He was a diver with his tank on his back.

 

[Subcooled]

This would have been a perfect topic for the Mythbusters.

True. Mythbusters is gone, though. You can blame Finland for this, as Hyneman came here to work on lesser things (pun intended).

The pressure wave is caused by the displacement of air immediately surrounding the bolt itself

due to heat

and the bolt dissipates very rapidly once it hits [...] the body of water.

Yes, but that current does enter the water, probably breaking it down to hydrogen and oxygen, or at least vaporize it, and surely 50 000 F air has an effect too (although the time is short). Doesn't this cause a (localized) pressure wave? Water is more dense, hence a blast wave would propagate much better in water than in air.

Even if a cohesive bolt could penetrate deeply into the water, the overpressure declines according to the inverse square law.

True. The decline would be fast.

Given that people have survived direct hits on dry land, a close hit in water might not be that bad (although it is relatively worse than in thin air).

I wouldn't want to be directly under a strike at my safety stop, but 30m under should be OK. Don't go testing it on my word though.

Hey, I found a testing lab:
Who's gonna go?

 

[Subcooled]

If your in a tank with sweet water in it, chance are the tank its self would be earthed. Providing the tank is large enough you wouldn't feel anything providing you were far enough away fromthe strike. Would depend on distance from the strike...either way probably not best to dive in a storm if it can be avoided.

I was diving in a stone quarry. The red granite rock certainly acts as an isulator (it's earthed by definition, though) and the sweet water doesn't conduct electricity much better. If a lightning strikes the waterbody, it will be 300 feet away max.

Wet person carrying metal would be a bit of a target for lighting strikes whilst getting out of the water.

Certainly, and especially with metal spiked objects.

You able to explain more on the situation if your in a tank? If so the size etc... Interesting topic

Just a plain sweet water body and a thunderstorm.

If conductivity would be infinite, things would be simple and spherical, right?
But when there's actual matter and resistance, it gets complicated.

Experimental proof would be valuable.