# Creature that swims in the solid ground

I have a moment in my story where the main character comes across a planet with "solid" swamps. Let me explain.

Basically, there are creatures here that can swim through the ground like it was some very thin liquid, however, when any other organism comes in contact with the substance, it's like walking on solid ground. This creature would be relatively large (around the size of a killer Whale) and prey on the other species that find themselves in the middle of these plots of solid alien swampland.

What are the possible organs, adaptations, and behaviors a creature like this would possess, along with what type of substance would exhibit this ability?

• Reminds me a bit of "Navy Day," a sci-fi short by Harry Harrison. Not really an amazing story; I can summarize it in a comment box: the army develops a field generator that makes it possible to cross water as though it were land (with tanks, troops, etc.) and claims this obsoletes the navy. The navy then develops a field generator to make land navigable as though it were water, e.g. by battleships. – Wildcard Aug 14 '17 at 1:57
• Can the ground be sand? If so, check out this guy – pipe Aug 14 '17 at 2:27
• Sounds like hortaculture to me... – Jim Garrison Aug 14 '17 at 3:46
• In StarCraft 2, the Zerg's ability to burrow - and move while burrowed in some cases - is explained thusly: They have billions of tiny muscles that vibrate at a low frequency, effectively loosening soil, crumbling rock, and snapping vegetation. It is later described as effectively 'swimming' through the ground, though not as fast as through water. Granted, most Zerg are quite a bit smaller than you're describing. Not sure how feasible an explanation this really is, but there's precedent in fiction for it already at the very least. – CGriffin Aug 14 '17 at 15:50
• This is of course, essentially Tremors – T.E.D. Aug 14 '17 at 16:22

Edit: I've incorporated some of the suggestions from the comments

I'm not sure how possible this would be in real life, but as you've not used science-based or hard science tags I think this should be believable enough.

What you're looking for is a Non-Newtonian Fluid. The most famous of these is probably corn starch in water (or custard, which often amounts to the same thing) which is a liquid but if enough pressure is applied to it it becomes solid and can be walked on, if you do it right. Now that's not quite what you are looking for, you want your unwary prey not to realize they are in a 'swamp' of sorts so needing to walk in a specific way is out of the question.

So here's where we start to play with things. We make the Non-Newtonian Fluid (let's call them NNFs for short) a lot thicker, so that instead of requiring careful high pressure movements to make it solid instead it's solid most of the time but if you move slowly and gently enough through it behaves like a liquid. Edit: Apparently this is possible even without any handwaving, what we need is called a shear thinning fluid - the faster you try to move it, the easier it is to do so. Thanks to Agent_L and Aliden in the comments

According to this website it is possible to swim in an NNF, and in fact it's easier the bigger you are. That suits us fine as you want a fairly large creature.

So lets look at the creature itself now. It needs to be making slow and gentle movements to maintain the liquidity of the NNF so it's not likely to be a chasing predator. Ambush seems much more likely and sensible. So we want a creature that waits under the surface for it's prey to walk over head before springing up. As pointed out by anaximander in the comments springing should work fine, even if it causes the NNF to solidify a large and strong enough creature should have no problem bursting through a thin layer of solid ground.
Waiting for prey to walk over head isn't the best strategy though, you want to lure your prey over. Conveniently your creature also probably needs some kind of snorkel like device to breathe (I'm not sure gills would be effective in an NNF) and we can combine that with a luring mechanism, something that rises up and sits above the ground (in fact maybe it grabs the prey and drags them down, which might be easier than springing up through the NNF).

The first thing that comes to mind is an Angler Fish, one of these beasties:

Other options suggested in the comments include; A snapping turtle like creature (suggested by Dent7777) - In real life snapping turtles already use a lure to hunt. Our creature would be a vastly scaled up version whose head was heavily camouflaged and disguised with a lure that sat inside it's open mouth. The head would sit above ground and wait for prey to enter the mouth before swallowing it.

A creature whose large mouth rises up to envelop it's prey and swallow them whole (as suggested by Andrew Cheong). I would imagine in this instance the creature would probably be snake like (indeed a Dune style sand worm, as mentioned in other answers, would fit the bill).

• This was awesome to read. Thanks a bunch. I have a fairly good idea about what I'm going to do now – LargeDan69 Aug 13 '17 at 21:22
• That last leap for the ambush can still be viable even if the fluid solidifies. There are creatures that bury themselves under thin layers of dirt or sand in order to ambush prey. Perhaps this creature has very strong fins, enough to burst out from what is essentially soil at that point, but it can't swim that way all the time because it would be incredibly tiring, so it saves it for that sudden strike when prey turns up. – anaximander Aug 14 '17 at 8:19
• Non-newtonian fluids also work the other way, eg mayo is solid, but when you hit it hard enough, it flows. A really thick mayo + a really powerful and fast whale = profit! – Agent_L Aug 14 '17 at 10:45
• @Agent_L yeah, I did think that was the case but the info I'd found wasn't 100% clear. Thanks for confirming that. – adaliabooks Aug 14 '17 at 11:08
• I am thinking your creature might be like a giant alien snapping turtle. Hell, those things look pretty alien as it is! They already have an established practice of lure hunting, so the adaptation is pretty believable. I am picturing their mouths resembling either an overturned tree with a tasty looking mushroom or a large lily pad with a flowering fruit in the middle. This would allow the creature to hunt without having to spring or accelerate quickly. It could move during the nighttime, repositioning itself or rearranging its environs to steer into its gaping maw. – Dent7777 Aug 14 '17 at 13:19

I would suggest a creature that can create enough vibrations around it to make sand behave like liquid.

https://youtu.be/zjgURBIqJ6s?t=2m15s

Then it would be relatively easy for it to move through because the sand will auto vibrate away when pushed against.

Explanation of the mechanics:

Soil liquefaction describes a phenomenon whereby a saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress, usually earthquake shaking or other sudden change in stress condition, causing it to behave like a liquid.

The phenomenon is most often observed in saturated, loose (low density or uncompacted), sandy soils. This is because a loose sand has a tendency to compress when a load is applied; dense sands by contrast tend to expand in volume or 'dilate'. If the soil is saturated by water, a condition that often exists when the soil is below the ground water table or sea level, then water fills the gaps between soil grains ('pore spaces'). In response to the soil compressing, this water increases in pressure and attempts to flow out from the soil to zones of low pressure (usually upward towards the ground surface). However, if the loading is rapidly applied and large enough, or is repeated many times (e.g. earthquake shaking, storm wave loading) such that it does not flow out in time before the next cycle of load is applied, the water pressures may build to an extent where they exceed the contact stresses between the grains of soil that keep them in contact with each other. These contacts between grains are the means by which the weight from buildings and overlying soil layers are transferred from the ground surface to layers of soil or rock at greater depths. This loss of soil structure causes it to lose all of its strength (the ability to transfer shear stress) and it may be observed to flow like a liquid (hence 'liquefaction').

As to what organs that creature should possess, I'd look at the crocodile, and expand that

https://gizmodo.com/im-amazed-by-what-happens-during-this-alligators-mating-1713932794

Crocodiles produce strong infrasound waves that sends water around them flying away.

The bellowing cycle of an American alligator. Starting with head and tail lifted in the so-called 'head oblique tail arched' (HOTA) position, and riding high in the water on inflated lungs, the animal sinks into the water as air is expelled through the larynx to create the bellow. Resonance driven by the sound produced makes the water dance from the flanks and then from the dorsum when it submerges towards the end of the event.

• This option has the benefit that it is science based. Liquefaction is something that actually does happen and can be devastating for objects in the area. The ground does not even need to be sand for this to work; I believe it can also work with loose dirt. – Loduwijk Aug 14 '17 at 18:27
• This could be a great answer if it were expanded into a full explanation of the mechanic. – Loduwijk Aug 14 '17 at 18:28
• better like this @Aaron? – Tschallacka Aug 15 '17 at 8:25
• Indeed. That extra bit about alligators makes it even more science-based. Great answer. – Loduwijk Aug 15 '17 at 20:00

The sandworm from Dune immediately popped into mind as the kind of creature you are looking for. Perhaps you can derive some inspiration from it.

A description of its physiology from Wikipedia: Sandworms are animals similar in appearance to colossal terrestrial annelids and in other ways to the lamprey. They are cylindrical worm-like creatures with a fearsome array of crystalline teeth that are used primarily for rasping rocks and sand. During his first close encounter with a sandworm in Dune, Paul Atreides notes, "Its mouth was some eighty meters in diameter ... crystal teeth with the curved shape of crysknives glinting around the rim ... the bellows breath of cinnamon, subtle aldehydes ... acids ..." https://en.wikipedia.org/wiki/Sandworm_(Dune)

• Do sandworms live only in sands? Does sand count as solid ground? – L.Dutch - Reinstate Monica Aug 14 '17 at 7:28
• Sand can be pretty solid. Sand bags used to build walls for cover from gun fire. But these creatures eat through rock too, hence their teeth. From that same physiology paragraph on wikipedia: Sandworms grow to hundreds of meters in length, with specimens observed over 400 metres (1,300 ft) long and 40 metres (130 ft) in diameter, although Paul becomes a sandrider by summoning a worm that "appeared to be" around half a league (2,778 meters = 9121 ft) or more in length. Saharan desert average depth 150m: piecubed.co.uk/sand-facts – Alan Ball Aug 14 '17 at 7:58
• Sandbags.. that's the point! Sand alone won't make a wall. – L.Dutch - Reinstate Monica Aug 14 '17 at 9:44
• @L.Dutch Well, I've walked on sand on numerous occasions without falling through it. While it's true that without the bag, the sand wouldn't keep a wall form, so do dirt and water. Still, the ground and the sea stay still, because there is nowhere to go for the dirt and water that isn't already filled with dirt and water. Sand makes a pretty solid ground because in order to fall through it, you have to move your volume of sand, which has to go somewhere. Water does because it has a fairly low viscosity, sand doesn't. – ksjohn Aug 14 '17 at 10:33
• Or the creatures from Tremors ... – ivanivan Aug 14 '17 at 13:35

The "swamps" are actually the bodies of massive fungal colonies. They developed a complex symbiotic relationship with small animals that would forage for food and then could be transported in an organic polymer matrix, sort of like the cytoskeletal transport networks in our own cells. This progressed over time to allow larger and larger creatures to interact with the network by releasing enzymes and signalling molecules to activate the network and break the polymer. These signals then swiftly degrade after the animal passes through (thanks to enzymes released by the fungus itself) and the polymer reforms.

I'm imagining it started with a relationship sort of like sea anenomes and clownfish, where the fungus provides protection (you can duck back inside to get away from predators) and the animals provide grooming/foraging services. The larger creatures are predators that evolved the ability to biochemically 'hack' the interface and therefore gain access to the prey that would try to hide. The larger animal has become essentially a parasite.

• I like this, it's completely left field which is always interesting. – Ash Aug 14 '17 at 17:56
• There are several really good answers posted, but this one immediately became my favorite halfway through the second sentence. Great idea. A "living ground" that can be moved through could be accomplished a few different ways, so it is easy to adapt this answer too. +2 – Loduwijk Aug 14 '17 at 18:36
• I particularly like this idea, especially because it gives you a nice opportunity for your characters to beat the system. Perhaps they find that animals who can enter the swamp tend to eat a particular mushroom that provides the enzymes, and they could douse their suit in mushroom extract to trick the fungus. I'm liking this idea more and more, imaging more of a dense plant-like area, and the plants shrink and recoil when exposed to the enzymes. – Bazul Aug 17 '17 at 15:15

It's probably easier to define an environment first and then work on a creature that fits into it. So I'm going to advocate for a peat bog, it's basically solid but, when healthy, it's so saturated that it can act like a liquid, especially if you add some localised energy in the form of vibration.

So what kind of creature swims through essentially solid peat? An Orca is actually a pretty good shape for this environment but I'd go a little thinner and longer with extended trilateral fins along most of the body, the fins ripple for added speed as well as angling for steering. It's going to use echolocation same as a dolphin except it's going to be a much more powerful vibration emitted from the whole body, this is going to create a liquefaction pocket around the beast allowing it to swim unimpeded. The liquid bubble around our "Land Whale" also serves another function, where it hits the surface the bog surface is going to go from solid but soggy to something the with the properties of tar sucking down prey. This creature could probably survive as a filter feeder and have gills but I think it's more interesting as an air breathing predator. I also like the idea of them hunting in pods like Orca or Dolphins so you'd see them breaching as a pod the way cetacea do in Earth's oceans.

You can turn rocks to liquid, if you have enough heat and not afraid of it - melt it.

There was a project for getting rid of nuclear fuel waste - put a lot of it in a big ball made of tungsten. Then heat from fission would heat it up to 3000K(at some sources number 1200C is mentioned, seems a bit low) which is below melting point of tungsten so it stays solid but way above melting point for most of rocks. Also, tungsten is more dense than most of the rocks, so it would sink and bury nuclear waste in the mantle.

Make this ball alive somehow and make it less dense so that it would not sink and you have it.

• Interesting answer, I would suggest placing documentation into it for more detailed information. – Reed Aug 14 '17 at 13:37
• Um okay except rocks are already solid, proverbially so in fact, this answer makes little sense and has no bearing on the question of a swampy land swimmer. – Ash Aug 14 '17 at 17:59

Another option that comes to mind is that the creature is incredibly dense, like neutron star material levels dense. So while such a thing wouldn't be possible in the real world, you might be able to get away with it in sci-fi.

By having your critter be so incredibly dense, things that are solid to us as humans would behave like fluids to this creature. Its body would literally just push dirty and rock aside like it was nothing, because relatively speaking, it is.

• @KingMagmaBlock, Making it out of neutron star material would shatter my suspension of disbelief. I suspect that it would shatter the suspension of disbelief of most people with a science background. It would be better to have it be some other unexplained substance/phenomenon. Saying it's made out of neutron star material, or even something that approaches that density, allows people to make assumptions as to how the substance behaves. For instance, that such a quantity would not have enough gravity to maintain that density. That it weights ~1.2x10^19kg, which would be...interesting, etc. – Makyen Aug 14 '17 at 1:42
• @Makyen I wasn't planning on making the creature's composition literal Neutron Star material, I more just liked the idea that the creature is dense enough to sink through the material I'm describing. I'm pretty sure if it had the mass of something like that, it would most likely die instantaneously, then cause unknown havoc to its own host planet. Thanks for the feedback, however – LargeDan69 Aug 14 '17 at 1:50
• Fishes/Killer Whales are not incredibly dense. You cannot swim if you are incredibly dense, you can just sink. Look at how difficult it is to maintain a plane in the air (speed + specifically design wings): that's because it is denser than air. – Matthieu M. Aug 14 '17 at 6:54
• This is not a great idea, it's terrible! If the critter was neutron star dense, then the whole planet whose swamp it was swimming through would end up smeared over the surface of the creature in a thin layer - it would not be pushed aside at all. And swimming creatures are fairly buoyant in the medium they swim through, meaning they are fairly close to having the same mean density as that medium. Otherwise they wouldn't swim, they would walk on the sea bed. – Grimm The Opiner Aug 14 '17 at 8:53
• There is absolutely no relation between density of the observer and state of the matter. Solid remains solid, even if your fish is "more solider". The forcing through rock you're describing requires sheer strength and crush resistance, but the fish overall could be as light as aerogel. There is no point of using the gravity to sink, because it means that the creature still has to have even more muscle power to overcome gravity to swim up. So it might be of neutral buoyancy and save half of the power just as well. Just what regular fish and submarines do. WORST.ANSWER.EVER. – Agent_L Aug 14 '17 at 10:58

In League of Legends there's a champion called Rek'sai. She's a voidborn (an alien from a different realm) and can 'swin' in the ground. She makes the ground vibrate enough to move freely through solid terrain but she also creates portals to travel faster. She's more like a cricket mole but she moves like a shark in the ground.

She's a feared monster in Shurima's desert who can eat expeditions like nothing:

She's massive, enough to eat camels with one bite

• The creatures should lack of eyes. Eyes would be a huge disadvantage when you're swimming through solid terrains
• Have an exceptionall smell/hearing
• Almost grills OR a blowhole to breath outside, this means they would have massive lungs.
• They must emite constant sound waves (like a purr to disperse the solid materials and swim freely)
• They mostly feel vibrations rather than sounds, since they're underground

A somewhat different approach: make creates that “glitch” through the solid ground. They don’t swim, per se; rather, they propel themselves forward by jerkily disappearing and reappearing (displacing whatever solid was in their place).

A (very hand-wavy) basis in solid science would be quantum tunnelling: you creatures have evolved a way of generating a coherent quantum field to be able to appear as a macroscopic quantum object, and to control the probability and direction of tunnelling their whole mass through the surrounding solid.

(Even more hand-wavy would be to rely on the creatures creating localised, temporary wormholes or some other form of teleportation.)

If you ever saw a mole dig himself into soft ground, swimming is not that far away.

This question instantly reminded me of Hugh Howey's Halfway Home. In the story, there are tunnel boring wormlike creatures who (if my memory serves me correctly) have an ability to absorb the materials they come into contact with - and then defectate them out the back end turning it into piles of diamonds/gold or something in the process!

Kind of questionable science, but potentially acheivable if the creature possesed some attributes of molecular nanotechnology (the Gray Goo springs to mind here!)

What about something like a giant, but thin amoeba? It would push it's 'membrane' forward in a sharp point, then flow into it from behind, forcing the membrane outward. If it were moving through sand or loose soil, it may leave a trail visible from the surface, but if it were more of a liquidy material it should flow around and fill in the gap behind.

Not sure how fast it would move, but it's your world...