system
Given the following post, respond as if you're commenting on Reddit:
human
When a highly poisonous marine organism dies, why doesn't the poison kill all the fish in the area?

The poison has to leak out from the poison sac eventually. Especially when a fish has enough poison to kill a hundred people, wouldn't it be deadly even when diluted by the sea water?
gpt
From a math perspective with no regards to the properties of animals or substances:

Assume a toxic fish can kill 100 adults and it contains 100ml of poison, so 1ml (1/100 of total poison) can kill one person.
 If the fish expels all of its poison at once, and it's diluted into a cubic meter of water, there will be 1000l of poisoned water. To receive a lethal dose, you'd have to consume 10 liters of poisonous water, so it would be less toxic (for a mammal) than beer alcohol content (or the overdose of water itself). 

So basically any realistic dilution - even assuming the poison sac explodes immediately instead of leaking out - will be too mild to be toxic to any animal even if they'd somehow consume 100% of the poison by swimming through it.