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Go to Brilliant.org/SciShow to learn more about their Classical Mechanics course. [♪ INTRO]. If you ever happen to find yourself in southwestern Australia, pour some water on a seemingly-empty spot of dirt.

You just might wind up with a pool full of teeny fish! Salamanderfish are tiny, long-bodied fish that are found only in the southwest corner of Western Australia in ephemeral pools that form on peat flats. The water they live in disappears in the summer months, from January to late May.

But that's no problem for these amazing little fish, as a pair of ichthyologists documented in a paper published in 1989. They were monitoring 22 pools to gain insights into salamanderfish, since there was very little known about this species. So, they were watching as the water levels got lower and lower, until finally, the pools dried up entirely.

But… there were no fish bodies left behind on the dry sand. Which was a bit perplexing. Then, the researchers dug down.

And there were the fish — alive — just hanging out in the sand on the water table. That's when the pair got an idea. They brought in a fire truck and artificially flooded the pools with two thousand liters of water.

Within minutes, live salamanderfish were swimming about. So, literally, instant fish—just add water! They've since found salamanderfish as far as 60 centimeters down in the sand.

That's a long way to dig when you're only a few centimeters long! But it makes sense, since these fish have bodies that are built for burrowing. Their wedge-shaped skulls can withstand the crushing pressure of the damp sand.

They also have extra space between their vertebrae and fewer ribs, both of which help them wriggle like a salamander — hence the common name. Of course, retreating under the sand only works if you can survive for months buried in the earth. So these fish have that figured out, too.

While they're hanging out in their burrows, waiting on the water to come back, they enter a dormant state called estivation. That's kind of like hibernation, except it occurs under hot, dry conditions. And they can stay alive for several months like this.

Since there isn't enough water in the sand to breathe with their gills, they use their skin instead. They also coat their eyes and genital openings with mucus, to protect these especially important bits from drying out. And, they don't eat.

They rely on stored fat. Just in case all of that wasn't hardcore enough, I feel like I should point out that even when there is water in their pools, it's pretty gnarly. Because of the breakdown of leaves and other organic matter, the water is dark brown and has an average pH of 4 — which is a thousand times more acidic than plain freshwater.

The pools also experience huge temperature swings, like from 16 to 34 degrees Celsius in a 24-hour period. So not only are these fish super-burrowers, they're ultimate survivors. And they've been at it for a long time.

They're the only species in their entire family, which split off from other fish about 240 million years ago! Of course, we've only just begun to learn about them in recent decades. Further research will almost certainly reveal other traits that help them live their extreme lives.

That is, if there are any salamanderfish to study. Unfortunately, climate change is further drying up their habitats. And that means, their next summer disappearing act could be forever— unless some humans step up and save them.

Thanks for watching this episode of SciShow! And thanks to today's sponsor, Brilliant. They offer fun, engaging courses in STEM topics— so, they can help you dig deeper into the topics we talk about on SciShow!

Like, if you want to appreciate the physics hurdles this fish has to overcome to burrow in the sand, you might try their Classical Mechanics course. You can gain access to it and their entire library of courses with their annual premium subscription. And you can get 20% off that subscription if you're one of the first 200 people to sign up at Brilliant.org/SciShow! [♪ OUTRO].