If I were to stand on my diving board during a
lightning storm and jump at the precise moment – that
is to say, the moment a violent lightning bolt hit the
pool and vaporized it – would I hit concrete?
I really do not believe that a lightning bolt has the energy flux and heat transfer available to vaporize the water in a swimming pool as you are thinking. This can be somewhat verified by observing the numerous times where lightning will strike the surface of a lake or pond, and there is not an appreciably large amount of vaporization that occurs.
This is precisely why they were able to find the Titanic. Finally, after years of waiting, a bolt of lightning hit the ocean. Then, they were able to fly mysterious black helicopters over the general vicinity of the sinking.
Now, we need lightning to strike near Atlantis, as well as in Loch Ness so that we can find out about that pesky Nessie once and for all.
First, why would you be going swimming during a lightning storm?
Second, if the pool holds enough water that you can dive in it, lightning would not vaporize.
Third, no need to hit the carriage return, the text will automatically wrap for you.
Fourth, how exactly do you pronounce your user name?
Perhaps vaporization wasn’t noticed because during a typical lightning storm humidity is nearly 100%. Supposing the air was dry, wouldn’t this significantly increase its capacity for holding water boiled from the pool?
[hijack]What would happen if you jumpedright before lightning hit you? Since you aren’t grounded would you feel anything?[/hijack]
If the current from a bolt can travel all the way from the clouds to the ground, even if I jumped, I imagine it could still make it from my toes to the diving board without much trouble. also, my name is pronounced however you would like to pronounce it.
I am certain that the energy required to vaporize an entire pool full of water exceeds that which might be found in your typical lightning strike.
Perhaps someone out there knows how much energy is required to reduce a gallon of water to vapour?
I’m sure this has happened in Western Australia on occasion, although it has been kept under wraps. 
Air temperatures around a lightning bolt range from 15,000 - 60,000[sup]o[/sup] F, and to answer mongrel’s question, I think considering the extreme temperature, being grounded or not may not help you survive.
However, and I’m not sure of this, but the lightning’s effect on water would be negligible, regardless of humidity. The lightning would hit the water and disperse while searching for ground.
The only thing I can find on a search, is this site which only says:
“Lightning on striking water has been known to throw up a plume of steam.”
A far cry from boiling away an entire pool.
This site explains a little more in depth about what happens when lightning strikes:
So, the current dissipates dramatically within a matter of less than a second. Not enough time to boil away a pool full of water. It is the flowing current of electrons which causes the heat, not the presence of the electrons themselves, and as the current is slowed the heat dramatically lessens.
Your best bet though, is to not swim during a lightning storm.
Not an expert on this, but lightning has such huge potential vs. ground that it tears right through the air to get there. Since you yourself are not grounded, the lightning would likely not go out of its way to hit you. But if you just coincidentally happened to be on the lightning’s path to ground then you would probably have the same amount current through you as if you were standing on the ground, with the corresponding damage.
You also have to consider the timing. Even if it was strong enough to theoretically boil away a swimming pool, it would take a while. Think of it this way: As the water begins to boil, the steam builds up in the area. It takes time to diffuse away. As the steam builds up, the local pressure would build. As pressure goes up, so does the boiling point of water. In other words, it takes progressively more and more energy to turn the next gram of water into steam. The required energy would get pretty large pretty fast.
Okay. So now we’re talking about a strong, long-lasting bolt of hot lightning hitting a smallish pool of water that is already heated to near boiling (thanks to the active volcano on which the pool happens to be located) under rather dry conditions and with a slight breeze to whisk away steam pressure…
…if only for the possibility that the impact of the strike would slosh the rest of the water out of the pool. I think my mind is now at ease with this issue.
Let’s see… two large surfaces (clouds and ground) with a large potential across them, and something small in the middle… that’s basically a very large bug zapper now isn’t it?
So, if you want to know what you would feel if you happened to jump above a pool at the same time as a lightning strike, ask yourself how a bug feels the next time you hear that zzzzaaaaaapppppp!!!
For your reference this is the new screen name for what was once xovoxovoxo. I was required to change my name by the moderator but I have yet to find out why. Perhaps this would be a good topic for the board?
Anyway, my original question assumed that I was still on the diving board when the lightning struck. Lightning follows the path of least resistance, but that doesn’t mean that it would hit me. As is evidenced by this close-range photograph, lightning does not always hit the tallest object or the most conductive:
I did some rough calculations, and assuming I didn’t make a major f***-up, I’d say there’s no way a lightning bolt could vaporize a whole swimming pool.
Pool volume = 47,300 l (that’s 24’x12’x6’ for the yanks)
Joules or watts to raise 1 kg of water 1 degree C: 4186
To start, say pool is at 20C (room temp)
Must raise it 80C: 80 degrees * 4186J/l/degree * 47,300l
= 1.584x10^10 J
Now Joules to vaporize 1 kg water = 2,260,000
Then vaporize this water: 2,260,000J/kg * 47,300l
= 1.07x10^11 J
Giving a grand total of 12.27x10^10 joules or watts of power to vaporize the pool starting from room temp.
Here’s the tricky part; I couldn’t find a good site that gave how much power is in a lightning bolt. I found numbers ranging from 4000 watts to 666,666 watts. Hell, say the lightning had a million watts, you’d still need over a hundred thousand lightning strikes to vaporize it all, not to mention the complications in the above posts.
(come to think of it, those numbers look mighty suspicious… that’s what you get for trying to do math with a cheap calculator at 3am… feel free to point out my errors)
I have no idea what to do with these figures, but I found them on the same page where I found the close-range photograph. They do not site a source but I distinctly recall hear/reading elsewhere that the heat of lightning could be compared in multiples of the sun’s surface temperature.
Voltage involved in initiating a cloud-to-ground strike: 100 million to 1 billion Volts
Average peak current in a cloud-to-ground lightning stroke: 100,000 Amperes
Average peak temperature of a lightning channel: 50,000° F (27,600° C)
Comparison- Average temperature of the sun’s surface: 11,000° F (6000° C)
Average duration of peak current in a lightning discharge: 1/1000 sec.
Estimated diameter of a lightning channel: 0.5 to 1 inches (1.3 to 2.5 cm)
Length of a cloud-to-ground lightning channel: 2 to 10 miles
I reckon the lightning would strike you even if you were in mid-air at the time; the electrical resistance between your head and your toes (or your toes and your head if you were diving) is far lower than the electrical resistance of air across the same distance; the lightning would strike you at one end and spark off you to ground.
I thought is was 1.2 gigawatt - that’s what they used in back to the future to power the flux capacitor 
Here is where I see your problems:
Assuming lightning would boil all the water away you whould be in a very high temp steam bath under pressure and would get extreem burns from superheated steam. Also there would be so much steam created all at once you would be explosivly blown into orbit (or at least into your neibors pool).
but I don’t think you would come close as:
1 water takes too much energy to convert to gas
2 the lightning would not hit the pool evenly so even if you did vaporize one ‘tunnel’ there will still be water around it.
3 Hi Opal
4 local pressure would increase preventing water from boiling