How does electrocution in water work?

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It’s well known that it’s deadly if you drop a toaster in a bathtub, but what happens if someone drops it in a large swimming pool? What happens when lightning strikes the ocean? Will it kill fish or people in the nearby vicinity? Also why does this electrocute you in the first place?

In: Physics

Let’s understand principles first.
1. The maximum current flow will occur along the path of least resistance.
That is it.

Now consider your first scenario.
In bathtub, when live wire(the one that is at high alternating voltage) touches the water, it will find the path of least resistance. This could be a path in water to say the drain pipe which is solid metal and is connected to your plumbing system which is usually at ground potential. Now this could provide a path of least resistance and you will not be harmed. However, say you or your limbs provide a path of least resistance, the current flow through your body will kill you because this amount of current actually generates a lot of heat which reduces your body’s resistance and allows more current to flow to cook you ‘ripe’. The case in swimming pool and bath tub is same except that the chances of current flowing to ground are high due to multiple holes dug in it(for electrical and plumbing outlets). The video in the following link will help you understand.

https://youtu.be/6Dd6_TghcE0

How does it kill?
Well the current basically wreaks havoc on your nervous system. Consider that you pass such high current through a wire that is not designed to tolerate such high current. This causes burns too since your body heats up. Also, major risk of electrocution is fibrillation. Consider, your heart like a drum beating at a constant rate and some powerful elephant grabs the drummer by its trunk and bangs him on the drum black and blue with its own random rhythm. Surely, your heart is not working as it should and this loss of rhythm is called fibrillation. This is what kills people in majority of scenarios due to electrocution.

Now let’s see how our friends in the ocean are doing.
When the lightning strikes ocean, the huge current flowing through atmosphere to the ocean which then discharges via path of least resistance. Now for current to harm fishes it actually has to travel below the surface where fishes usually are.

Also majority of the current flows along the surface of water. ( I will try to get back to you with
ELI5 version of this).
Hence the current harms only certain fish within the area.
The following link discusses the probability of harm.
https://youtu.be/-9dNmFEn3iY