Most of us probably realize that this is quite a challenge. Simply holding them under for a long period of time will not do the trick. You can try dropping a freshwater fish in the ocean, but it's so hard to keep track of them there; the little buggers swim away! Since the question "how to drown a fish" is something that keeps everybody up all night, I've decided to bring you the answer and cure your insomnia.

My First Hypothesis
It is possible.

My Second Hypothesis
Drowning in air doesn't count.

Things You'll Need:
I know you're gonna wanna try it!

1. A Fish
2. A Fish Tank
3. Water
4. Maybe many more fish
5. Optional: instead of water, use oil or something... but that's too easy.

So, let's get started. Put the water in the fish tank, and put the fish in. They seem to like it that way. So far nothing out of the ordinary, right?

Next, don't put one of those oxygen pumping thingies in the fish tank. You'll notice it's not on the list of things you'll need. Why do you think pet stores sell them? Fish need them! (Also, don't put any plants in the water; they are also not on the list.)

Finally, to speed up the process, put many more fish in the tank. Try not to splash the water, and if you can, make sure the fish don't do it either. The more fish you put in the tank, the quicker they will use up the oxygen in the water. It's quite funny, because many people do this by accident. People have been drowning fish for years without even knowing it.

You'll see that after a while, the fish might actually "come up for air", which is not what most fish are designed for, and eventually they will suffocate in the water. That means they drown; I looked it up, and suffocating in the water is a good definition of drowning.

By the way, I haven't actually done this (on purpose), and I also don't encourage murdering animals, no matter how fun it might seem. This is a purely educational Rambling. Class dismissed.

I Wonder Why Fish Don't Drown: And Other Neat Facts About Underwater Animals (I Wonder Series)