The merfolk are fully marine creatures with a mix of human and piscine traits. The culture in question is demersal, and constructs cities and towns upon the sea-floor. The merfolk all have a finned tail like a fish and gills to breathe underwater. Most of them also have lungs or air-spaces for buoyancy, but a few don't. All of the merfolk need sleep, though not as much as a human. There are other citizens of the society, including manta rays, octopodes, and rarely some cetaceans too

Would this merfolk society have any use for beds (as something for people to sleep on), or would they have no need for soft sleeping places?

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    $\begingroup$ What, no seabed/riverbed jokes!? $\endgroup$ Feb 25 at 2:37

5 Answers 5


A bed is nothing more than a word that describes a comfortable (and, perhaps, safe) place to sleep. So...

Let's start with what we know

So What is Sleeping, Exactly?

Before we discuss fish sleep, lets figure build a platform by first deciding what sleep is.

The French psychologist, Henri Piéron laid down the definition of sleep in 1913 that is still used today:

– A stereotypic or species-specific sleep posture. We’re used to this in mammals. Most of them lay down in order to sleep.

– Maintenance of behavioral quiescence. In other words, the animal becomes inactive or dormant. It doesn’t eat or move around a bunch.

– Elevation of arousal threshold for stimulus. That is fancy scientist talk for the animal being less aware of its surroundings and not reacting as strongly to a stimulus.

For example, someone could walk into a room and say your name when you were awake, and you would immediately react. But, if you’re sleeping, someone might need to say your name several times, and loudly, for you to react at all.

– The state must be reversible. So, if you give an animal enough stimulation, it will wake up. This distinguishes sleep from things like being knocked unconscious or slipping into a coma.

No matter what kind of stimulus you give, someone in a coma will not simply wake up. So it’s different from just sleeping. (Source)

Summary: (a) There's a posture specific to your Merfolk. (b) They will be quiescent. (c) The could be less alert, but hold that thought. (d) And they can be awakened.

Next: do fish sleep?

The nature of fish "sleep" is an area of active research. While fish do not sleep in the same way that land mammals sleep, most fish do rest.

Research shows that fish may reduce their activity and metabolism while remaining alert to danger. Some fish float in place, some wedge themselves into a secure spot in the mud or coral, and some even locate a suitable nest. These periods of "suspended animation" may perform the same restorative functions as sleep does in people. (Source)

There's the issue with (c) above. Fish tend to remain more alert than mammals. But, to return to that first source:

Sleeping Posture: When fish sleep, they lie on the bottom, in a plant or hover almost motionless when they’re sleeping.

Dormancy: A sleeping fish will stop swimming, or swim very little, and stop eating.

Unresponsive: A sleeping fish won’t react to someone walking up to the tank, peering over the surface of the water, or food being dropped in the water.

You Can Wake Them Up: It is possible to wake a sleeping fish. Enough light or noise will eventually get them to wake up.

What changes might we care about with an intelligent species?

The semi-alert state that fish experience when asleep is to protect them from danger. Not just from predators (but that's certainly an issue), but also from stuff moving around. Currents carry things. Sometimes sharp pointy things like sticks. Granted, your merfolk might be deep enough that a stick isn't much of a threat, but they evolved, right? And that evolution would have had basic survival traits that would appear in current behavior.

Finally, let's return to my first statement and ask, what's a bed?

I've personally seen fish sleeping in stands of grass. But I've also seen a whole school of trout asleep in a shallow section of river, no more than an inch of water above them, swimming automatically to remain stationary in the water — and in the warm sunlight.

And that discrepancy invites a problem. You haven't explained how your merfolk react to sunlight. But let's set that aside. You do explain that they're city builders.


  1. They'll prefer to rest indoors most of the time for privacy and protection of both possessions and family.

  2. Being inside, currents are not longer an issue (at least not any more than human heating/air conditioning would cause).

  3. They are in a medium that promotes 3D travel. That means they'll want to secure themselves. IMO, most intelligent creatures aren't fond of super-tight spaces, so I'm not inclined to believe they'll build closets to sleep in.

  4. They will appreciate comfort, and comfort for a fish is warm and safe,so I'm thinking a warming source combined with natural plant life, which will hold them in place just fine. They won't float up because (a) fish don't do that when they sleep unless there's a current to move them and (b) there's a roof.

What's a bed?

  • A stand of plant life: grass, kelp, I can imagine pride would lead to a desire for rare plants to sleep in, but I can also imagine plant texture and the equivalent of underwater odor would also contribute to desirability. The plants will be periodically replaced, despite having been planted in the floor of the room, to keep them fresh (not unlike buying a new mattress).

  • Water conditioning: meaning freshness, oxygenation, salinity, mineral content, biological content (hey, they're merfolk, do they have gills? This could be a food source), and temperature.

The real question here is what they'd use as an alarm clock. Work starts at eight, after all.


Their beds would be 3d

Humans don't even need beds. They're just comfy. Merfolk would likely want comfort as well. However, underwater it's like you're constantly flying so a 2 dimensional bed just makes little sense. You can float in any direction. As such, their beds would be three dimensional.

Much like astronauts, they'd use sleeping bags.

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In space you float just like underwater so what you need is a cozy space where you're safe from floating things and a tight blanket to wrap around you. This is warm, comfy, and lets you sleep somewhat safe from small predators biting most of you.

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    $\begingroup$ This would also serve to limit convection currents that would cause unwelcome changes in temperature near a person's skin. $\endgroup$ Feb 24 at 18:44

Not for something soft. They would be not-very-far from neutral buoyancy. The farther you are from neutral the more you have to work to just hang around. So they would be adapted to being pretty close to floating without effort. Their net weight is pretty close to zero.

Probably not for warmth, either. They will probably be adapted to the local water temperature. Otherwise they will move.

But they might well need beds for other purposes.

For example, there is likely to be at least a little movement of the water. They will want to be secured in some manner so that they are still in the same spot when they wake. That water current is good also because when they are sleeping they won't be swimming. So they need some water moving by to bring them oxygen. So they will want something that keeps them in one location. But it also needs to be comfortable. And they won't want anything that will get tangled. So something like a thin net held down by something springy. Maybe only over part of them, just enough to keep them from floating away.

They might also feel more secure with some sort of protection when asleep. After all, they can't be watching for whatever dangers exist when they are sleeping. A bed in a bedroom might provide just enough protection. Maybe when a shark (or whatever) tries to get at them while they are sleeping, the process of breaking through a wall makes enough noise to wake them.

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    $\begingroup$ this would be why otter wrap themselves in seaweed when sleeping. $\endgroup$
    – John
    Feb 24 at 20:58

Where a merman resides, and feels safety inside, like a moray

So yeah, moray eels. They're predators, but they aren't nearly as large or as fast as other things out there, and they'd make a tasty meal for a reef shark. So they hide themselves in a convenient hole, ideally one which fits the eel fairly neatly, and wait for things to come past within the range of a quick sprint from their hole. And if anything does stick its nose in the hole, it's met by a mouthful of sharp teeth. Most things know that trying to extract a moray from a hole isn't a fight that's worth the pain.

It seems pretty likely that mermen would be in a similar position. They might be better swimmers than humans, but they're not better swimmers than a barracuda. Smaller fish can scurry for any cover, but if you're bigger then you can't rely on there being a suitable sized hole, so when you find one then you hang out there for safety. With a small opening to your hole, you're ready to spear anything that tries to get in and get you.

As mermen became more sophisticated and intelligent, they would likely have developed secure structures to keep their whole family group safe. Still though, the basic desire to be secure in their personal hole will likely remain baked into their instincts. It wouldn't be so much to sleep on as sleep in - think of the wall of body spaces in a morgue, perhaps, just with the handles on the inside. Still, it'd be recognisable as a sleeping space in the same way as a bed is.


If they can control their buoyancy, they won't need anything to sleep on since they can simply float above the ground, even when resting.

They would probably only need a safe environment, unless they sleep with half a brain at a time to keep alert.


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