Lightning

[Charged]

I was 40' down in a local quarry when suddenly a random diver appears out of nowhere. Tells us to surface, when we get there, a storm "was a brew'in". He just tried to warn us of the storm. Said they seen a couple bolts of lightning.

So it got me thinking. Is it safer underwater than topside? What do you do if your got in the water during a storm? Would I have been better off staying at 40' and continue diving....or swim back to shore from the surface?

 

[LeadTurn_SD]

I was 40' down in a local quarry when suddenly a random diver appears out of nowhere. Tells us to surface, when we get there, a storm "was a brew'in". He just tried to warn us of the storm. Said they seen a couple bolts of lightning.

So it got me thinking. Is it safer underwater than topside? What do you do if your got in the water during a storm? Would I have been better off staying at 40' and continue diving....or swim back to shore from the surface?

I've been told that out of the water is the best bet in most cases if possible.

I've read (can't remember where) of divers deep in a cave getting a pretty good jolt when lightning struck on the surface of the water, far from where they were... water is a good conducter.

I'm really not sure how deep you'd need to be, but 40' directly beneath a lightining strike may not be enough? :shocked2:

I don't know. Maybe a meteorologist will chime in soon....

Best wishes.

 

[Drewski]

This is an opinion on the subject, with some scientific fact:

Lightning and Diving

I have been in seawater less than 30 FT deep with multiple lightning strikes to a partially submerged rock jetty less than 20 YDS away. Loud as hell when I surfaced to see what all the flashes were then immediately headed back to the bottom. Not even a twitch.

Similarly, as a paramedic, I defibrillated a patient at 460J while standing in ankle deep water next to the patient. The patient had a cardiac arrest in the middle of a thunderstorm and was lying in a parking lot. For you PM types out there, it was a LP 5 with paddles on bare wet skin and a LOT of pressure. Again, not even a twitch.

Remember, electricity can be your friend!

 

[jeffloughridge]

That is a good question. When ENG Truck crews are trained to avoid overhead wires near their masts, they are also taught that if their mast does contact overhead wires and they are standing outside to keep their feet as close together as possible.

This is because with alternating current, the voltage radiates out like ripples on a pond if you drop a rock in. As it moves through the ground it decreases. If you have one foot in one spot, and the other just a small distance away, the voltage drop between the two spots is enough to kill you.

Water is actually a poor conductor of electricity. We use deionized water (and Dowtherm SR-1) as a coolant around tubes with 25,000 vdc on them. It's insulated, but if the water conducted it would short. It is the minerals and impurities in water that make it conduct.

Lightning is direct current so I would worry about the resistance of the water causing a voltage drop as it dissipates. If your head is at one point and your feet at another, your body could resemble a fuse.

This assumes fresh water...salt water is an excellent conductor due to the salt.

 

[Crush]

From a perfectly physical perspective, electricity takes the path of least resistance. This is why many people who survive lightning strikes are found naked and burned, but alive - the electricity flowed around their bodies, through wet clothing and along wet (salty) skin, causing the water to boil and their cloths to blow off. Many lightning fatalities are found perfectly clothed - their dry skin and cloths did not conduct, therefore the lightning went through them.

From that perspective, being immersed in a conducting medium - good stuff! Fresh water is good (fresh lake water conducts well - there are many impurities), but salt water is even better.

Later edit: The above situation assumes that you are not wearing any metal. Obviously this is not the case if you are diving. To a crude approximation, our tank will "attract" lightning (by having charge induced in it by the developing lightning discharge), but this charge will be over a factor of 80 times more intense where your tank is exposed to the air as opposed to being immersed in water.

 

[LeadTurn_SD]

Drewski,

Thanks for the link! That sounds pretty hairy (your experience with lightning).

I have read of one dive fatality (diver in water, but on the surface, ocean dive) due to a lightning strike. The link you posted seems to suggest that the lethal area for a lightning strike may primarily be the surface... that is interesting (and again, I have no knowledge other than what I've read).

Best wishes.

 

[Doubler]

I have been on night dives when lightening storms kicked up. I remember watching in awe the beauty of the storm at sixty feet. I have no scientific facts but I assume that while water is a good conductor the charge is dissipated across the surface as it is the path of least resistance and does not travel further than a few inches down. I believe being on the surface would be an extremely hazardous situation but being submerged would be relatively safe. Has anyone seen dead fish on the surface after a lightening strike? I know I haven't. My 2 cents.

 

[acwest]

I was 40' down in a local quarry when suddenly a random diver appears out of nowhere. Tells us to surface, when we get there, a storm "was a brew'in". He just tried to warn us of the storm. Said they seen a couple bolts of lightning.

So it got me thinking. Is it safer underwater than topside? What do you do if your got in the water during a storm? Would I have been better off staying at 40' and continue diving....or swim back to shore from the surface?

Being out and away from the water is probably best, but if the choice is between a surface swim or being on the bottom, you DON'T want to be the highest point in the neighbourhood...
-Craig

 

[Tanked]

Similarly, as a paramedic, I defibrillated a patient at 460J while standing in ankle deep water next to the patient. The patient had a cardiac arrest in the middle of a thunderstorm and was lying in a parking lot. For you PM types out there, it was a LP 5 with paddles on bare wet skin and a LOT of pressure. Again, not even a twitch.

Remember, electricity can be your friend!

I hope you mean 360 joules, and you wern't actually touching the patient when the shock was delivered

 

[captain]

Men can work on energized 230,000 volt and higher power lines by being brought to them by helicopter just as a bird lands on a wire. The reason they can do this is the same reason birds can perch on a bare wire and not get electrocuted, they become charged to the same voltage potential as the wire. Submerged in the water a diver would be in the same position, the lighting would charge the water and the diver to the same voltage potential. When voltage potential is equal no electricity can flow through the body. If any part of the diver is out of the water than the voltage potential becomes unequal which results in electrical flow through the part if the body that is out of the water to the water. Stay submerged but off the bottom or get completely out.