but there's an invasive fish here in the U.S.

that breathes out of the water and walks across land.

What the hell is going on?

I called Pam Fuller and Matt Nelson.

- [Lady On Phone] Hello, we're here.

- [Voiceover] Both fish biologists,

who study non-indigenous aquatic species

'cause I want to talk to them about

this straight up, badass fish.

- [Lady On Phone] The proper name for it

is actually Northern Snake head.

- [Voiceover] Thanks, Pam.

When the Northern Snake head was found

on the eastern U.S. coast in 2002,

the media went crazy, because this fish was named

one of the most invasive species to date.

Its origins are in Asia, but scientists

aren't sure how it got here.

Some say it may have escaped a fish market,

like, walked off and made it into a nearby stream

where it found a new and suitable home.

And this wouldn't have been hard.

Here's why.

If you were to make a successful invasive species

checklist, this fish checks every single box.

- [Lady On Phone] Lots of progeny, parental care,

broad thermal tolerance.

- [Voiceover] Meaning they make lots of babies that survive,

can live almost anywhere, and eat almost anything.

- [Man On Phone] Whatever they can

fit in their mouth, they're gonna eat.

- [Voiceover] And they can breathe out of the water.

How is this even possible?

Matt told me Northern Snake heads are called

obligate air breathers, which means

they must breathe on the surface periodically

in order to survive.

- [Man On Phone] They have a chamber kind of

in the back of their mouth, kind of behind where

the gills are, you can think of it

kind of like a very rudimentary lung,

and that allows the fish to extract oxygen out of the air.

- [Voiceover] And because they can breathe air,

they can crawl out of whatever body of water they're in

and into another, where say, there might be more food.

Even if that trek takes them a few days.

The Northern Snake head has a firm hold in our rivers'

ecosystems, much to the dismay of ecologists.

And while fishing has helped control its populations,

these guys are here to stay.