Being an ex-lifeguard (a long long long time ago), I know that when I was guarding an outside pool, at the first sight of rain, we cleared it because if lightning hit the water, the swimmers would be killed.
So, I can totally understand her question...
Now, unlike her, things like this drive me crazy! Thank God we live in a time where if you have almost any question at all - and it's likely that someone else in the world is wondering the same thing - the answer is sitting at your fingertips!
So I looked into it, and right away in google before I could even finish typing my question, there it was having been typed by someone previously!
Here are a few of the answers I found (as per WikiAnswers):
"1. Fish do get fried if they happen to be in the area of the strike, but because the ocean is vast and lightning is dispersed into the water for only a very short distance, most fish are only stunned. If lightning was able to travel in water and not be dispersed, would you want to go to the beach?"
"2. They do. Every year around 7,000-10,000 lightnings strike the sea around the world and when this happens most of Earth's marine life dies. Luckily fish are fond of sexual intercourse and the sea life grows to its peak numbers around summertime."TECHNICAL MORE COMPLICATED ANSWER
"My answer is two fold. First of all pure water is an insulator. When it is mixed with impurities those impurities are actually the conductors, not the water. Second electricity always takes the path of least resistance (It will travel through the material that is most conductive).--jackandcokewithalime
If you're in a pool of water and the lightning strikes most of the charge won't travel through the water, because it is an insulator. It will travel through you the conductor. You are the path of least resistance (especially if you're touching the bottom of the pool or the side of it). That is why people are killed in a pool from lightning strikes. Most of the people that survive such strikes were probably floating in the water, not touching anything else but the water (thus not completing a circuit).
I would suggest that most fish in the ocean do not get killed for this reason. Salt water is a very good conductor and as such the salt water pulls the path of the electricity from the lightning bolt AROUND the fish, not through it. I would add this as another reason amongst the others above.
When someone is in a bath tub and an electrical item is drop in and that someone is electrocuted, this is because the path of least resistance is through the person touching the bottom and sides of the tub. The water is mostly insulated from the current so it travels almost entirely through the human body."
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