Growing up, I was told to exit the pool when there was rain. It makes sense- relatively small volume of water + significant voltage can conclude pool day pretty quick.
But what about the ocean? If water conducts electricity, how does lightning not spread to every beach all the time?
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I believe you are underestimating the sheer insane amount of water that exists in the oceans.
The surface of the entire planet is proportionally more water than land and the oceans are deeper than our tallest mountains.
Any light you turn on or sound you make can travel indefinitely. But just like light is attenuated by being absorbed slightly in the air, and just like sound is attenuated by friction as it travels through materials, electricity is attenuated by the low (but not zero) resistance of the conductors it’s traveling through.
In a sense it kind of does. But the amount of current through any given bit of water is negligible because of how much there is. So if you are in the water any distance away from the strike, the voltage difference between one side of your body and the other is really small so there’s no shock. The current just flows around you.
But how good of a conductor of electricity is salt water?
Basically it gets “diluted”, the lightning travels in all directions through the water so as the volume of water that it passes through increases the charge decreases.
There’s a good discussion of some lightning safety questions at https://what-if.xkcd.com/16/
The sentence that has most stuck with me is “Water is conductive, but that’s not the biggest problem—the biggest problem is that if you’re swimming, your head is poking up from a large flat surface.”
The further the electricity travels through the water, the more its strength gets spread out. So lightning safety is mainly about being far enough away from the places it’s likely to strike that whatever amount of energy makes it to you will be negligible.
Electricity when traveling through any matter interacts with the matter and meets resistance. It also goes in the direction of least resistance, like milk spilled on the floor and it finds all the cracks. Resistance normally is electricity turning into heat. For people being in the water and how dangerous it is, it comes in two parts, one each lighting bolt is two lighting bolts one coming from the sky and a second one coming from the water as your head is more conductive than air is a great conductor and if it is the path of lease resistance can make you are target, second lightning has so much power in it that it can easily kill fish for hundreds of meters around a strike while all is takes to kill a person is 5 milliamps to the heart.
Electricity, radiation, heat, lots of other forms of energy transfer all attenuate as the inverse square of distance. Near the lightning strike all that electric current travels through a small volume to a larger shell of water surrounding the small volume, then from that shell to the next shell out, and so on. The current density is equal to the current divided by the cross sectional area of the shell. Like an onion, the farther away from the middle you get, the larger the shell area gets. When you get far enough away from the strike location the cross sectional area is so large that the current density is practically zero.
On top of the inverse square attenuation, some of the energy changes from electrical energy to heat along every increment of distance.
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