And, uh-oh, it's venomous.

How long have you got?

Well, that depends on a few factors, including the potency, dose delivered, and speed of distribution.

Turns out, not all venoms act the same way.

Here are the animals with the fastest acting venom on earth.

First up, spiders.

There are around 40,000 species of spider and most are venomous.

But, thankfully, only a handful pose a threat to humans, including the male Sydney Funnel-web Spider.

Its venom is 60 times as potent as cyanide and can kill a human in one to two hours.

The venom attacks the nervous system, kicking it into overdrive until, ultimately, it shuts down.

Of course, spiders aren't the only venomous animals in Australia.

It's home to 20 of the world's 25 deadliest snakes, including the Eastern Brown Snake which is responsible for the most snakebite deaths in the country.

Its venom is 8,000 times stronger than cyanide and can kill a human in about one hour.

Its venom also attacks the central nervous system but, this time, it slows everything down.

And, to top it off, the venom has a coagulant that causes the blood in your veins and arteries to clot.

Between the two, it's not a good way to go.

Now, at this point, you might consider switching your Australian safari to a scuba dive, just to be on the safe side.

But, venomous animals live in Australian waters too, like the Blue-ringed Octopus.

Its venom is 1,000 times more toxic than cyanide and it'll bring down a human in just 20 to 40 minutes.

Bacteria in its saliva makes an extremely potent neurotoxin which paralyzes your muscles.

And, once that paralysis hits your diaphragm and rib muscles, you have only a few minutes before you suffocate to death.

But another marine animal is even deadlier.

The fastest acting venom on earth belongs to the Australian Box Jellyfish, or Sea Wasp.

It's not the most potent venom out there at 2,000 times stronger than cyanide, but encounter one of these guys and you'll be dead in 15 minutes.

That's because their tentacles are covered with tiny, venom-loaded darts called nematocysts, which shoot heart-stopping toxins into the body wherever they make contact.

All of this sounds pretty scary but, remember, you're less likely to die by venomous spider than by car crashes and infection, or disease.

And, it's not like these animals are after you anyway.

They'd just as well prefer that you stick to your own habitat.

But, still, be smart, be respectful, be safe.

Tell us the scariest animal encounter you've ever had, and thanks for watching.