I want to develop a water-dwelling, intelligent species that could ultimately reach space.1 My question here is about the biology of such creatures.

I want my creatures to live in the water, not move onto land, but shorter outings onto land not only would be ok but would help my plot. This makes me think somewhat of whales and dolphins, which breathe air, live in water, and cannot survive long on land (at least without special intervention).

But whales and dolphins don't have anything like hands, and tool use is an important step along the progression that leads to advanced technology. While some dolphins use tools, capacity without something like hands seems limited. (If I am suffering a failure of imagination, feel free to challenge this in an answer!) We know that amphibious creatures can evolve hand-like parts; none of the examples there are very advanced, so I don't know to what extent this "goes with" the other developments I need.

Access to land implies some mobility on land. I assume this means something like legs (with flippers?). My creatures are native to the water, so it makes sense to me that mobility on land would be harder, but it should be possible.

I'm not looking for magical approaches like selkies.

How should I approach the biology of my water-dwellers? What combinations of breathing methods, appendages for tool use, appendages for mobility, and developments that support intelligence are most plausible?

I am aware of this question, which asks how a deep-sea civilization would evolve in a particular environment. I'm willing to adapt my environment to fit my creatures, rather than going the other way around, so while that question is somewhat helpful to me, I don't think it's a duplicate. I'm also aware of questions like this one and this one, which are about technological development but not about biology.

1 For purposes of my story they don't need to develop spaceflight, just use it. The water-dwellers want to leave their planet because the land-dwellers have polluted their environment beyond repair. If they can steal a ship from the land-dwellers and adapt its environment for their needs, that's fine. But they need to be advanced enough to operate it.

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    $\begingroup$ @cobaltduck -- you totally went down the same path.. Otto is so very cool! I wonder that whatever creature OP selects, could they not use other creatures as humans do -- horses for transportation, monkeys for picking coconuts, to do some of the things that they are not physically able to do? $\endgroup$
    – WRX
    Commented Dec 28, 2016 at 17:34
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    $\begingroup$ @MonicaCellio the answer is octopus. Here's link that might not come up in a search for hands, which are essential for tool use and the kind of development you are talking about: worldbuilding.stackexchange.com/questions/51689/… $\endgroup$ Commented Dec 28, 2016 at 17:57
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    $\begingroup$ The book Startide Rising from the Uplift series has space-faring cetaceans (neo-dolphins). They were engineered by humans (hence, uplift) but might give you some ideas on how they might operate spaceships and explore land. Plus it won both a Hugo and Nebula... $\endgroup$ Commented Dec 28, 2016 at 21:25
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    $\begingroup$ I saw the question and immediately thought cephalopods...they use tools and are highly intelligent. Only issue is how would they use electricity being a water-dwelling species... Check out the Mon Calamari in Star Wars. They're basically octopodes who somehow evolved a human body LOL. $\endgroup$ Commented Dec 28, 2016 at 21:26
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    $\begingroup$ The main limitation I see to this question is that all the answers require that they eventually be capable of living on land - i.e., not solely ocean-dwelling. And that's for a number of reasons - for example I don't think the ocean would be a good environment for metallurgy. $\endgroup$ Commented Dec 28, 2016 at 23:35

8 Answers 8


As far as we are currently aware, the most intelligent things in the oceans are the cetaceans (dolphins and whales) and the pinnipeds (seals, walrus, sea lions). Further, it is more tempting to want creatures close to us biologically to behave more like us as well, especially in fiction. Again, the closest cousins to hominids in the oceans are cetaceans and pinnipeds.

However, if you want something alive today to reach the point of being able to drive a space craft, I think you need a cephalopod (octopus, squid, cuttlefish).

As the linked Wikipedia article describes, many cephalopods have demonstrated spatial reasoning, puzzle solving ability, tool use, dexterity, and communication1. The larger ones have brains as big as ours.

Also, as another answer confirms, cetaceans need their flippers and specific body plan for speed and agility while swimming, and to chase down their prey- even those who only eat krill. Evolving any part of themselves for gripping and dexterity would come at extreme cost elsewhere. The same would be true for pinnipeds, who already have hardship enough hauling out on a beach to mate.

Other fiction works have explored a future where cephalopods continue to evolve and advance, such as the speculative squibbon. For the most part, they come to the same conclusion- there is nothing to prevent these creatures from ultimately becoming as capable as humans of manipulating their environment.

To get to the point where one can flood the compartment of a Saturn V and take the controls is not that much of a logical leap. I would expect the first ones to begin the charge would be ones in captivity, where we are already teaching them to open jars, take photographs, and predict soccer matches.

Edit: I almost forgot: http://xkcd.com/520/

1All the more impressive given that their "language" consists of changing their body color!

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    $\begingroup$ Cephalopods use tools, dolphins do not. Claim dolphins are more intelligent is thus iffy. Maybe our intelligence tests are too mammal-centric? $\endgroup$
    – Mołot
    Commented Dec 28, 2016 at 16:55
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    $\begingroup$ @Mołot - I argue that a bubble net is a tool. $\endgroup$
    – cobaltduck
    Commented Dec 28, 2016 at 16:59
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    $\begingroup$ @Mołot some dolphins in Australia have been observed picking up basket sponges to use in foraging around in silt - the sponge protects their nose from scrapes and potential stings as they root around for prey. Additionally they have been seen in several areas using conch shells to scoop up fish, though I'm hazy on the details about how exactly that is effective for them. $\endgroup$ Commented Dec 28, 2016 at 19:26
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    $\begingroup$ I don't think Paul was particularly trained for his predictions. $\endgroup$ Commented Dec 28, 2016 at 21:56
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    $\begingroup$ @ArturoTorresSánchez - That part was a joke. $\endgroup$
    – cobaltduck
    Commented Dec 29, 2016 at 0:48

Evolutionary biology: the first effective tool user wins.
In most marine environments two issues dominate most niches: (1) obtaining food and (2) not becoming food. I posit that your creatures will need to become tool users on their way to space. In that case, my intuition is to look at where/how tool using would give them an advantage earlier on.

I posit that the first creature (in your planet's large waters) to use tools effectively for getting food and self defense would out-compete the competition, thus having claws, tentacles or other dexterous appendages is a good starting point. Imagine either crabs or cephalopods wielding sharpened razor clams or augur shells (long, thin cones) as weapons against prey or would-be predators. Sharpening a shell (or bone) on the right kind of exposed rock is plausible underwater.

Side question: Is the chemistry of these waters such that any native (in elemental form) metals might persist long enough underwater to be used? Perhaps as a side effect of a recently dormant underwater volcano? (Or a plant species that conveniently concentrates/precipitates some metal?) Metals are probably essential to any non-handwavium, non-magical spaceflight. Native copper was a big trade item, before the iron age.

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    $\begingroup$ many metals last underwater as long as you keep it underwater. $\endgroup$
    – John
    Commented Dec 29, 2016 at 5:42

salamander-people or crabs

the hardest part is getting a water breather that can also build on land. Nothing intelligent fits the bill, so what does fit the bill: walking bottom dweller or something with a staged life cycle.

Crabs can come out on land for extended periods and have grasping appendages, exoskeleton is size limiting however so they should be dog sized at best. And they won't end up looking much like crabs.

Some amphibian like certain salamanders start out as aquatic but gain more and more terrestrial features as they develop. You could push this to the extreme and have a organism that is aquatic but becomes semi aquatic when it reaches sexual maturity. If their prematurity part of their life cycle is long you would have a creature that builds most of its civilization under water but the older ones can venture out onto land. There are extinct scaly amphibians that fit the bill. But you have a lot of flexibility with this approach and can create your creature to suit your needs.

I always liked the idea of a elongate six limbed scaly amphibians where the first two limbs function for grasping and the second set function for both grasping and locomotion. I used that as DM.

  • $\begingroup$ Salamanders are an excellent suggestion for future tool users though I think Crabs are not. Crabs are very primitive organisms, far behind most other marine life their size in neural complexity. Some of their near relatives even lack a defined brain. $\endgroup$
    – bp.
    Commented Dec 29, 2016 at 15:53
  • $\begingroup$ I mentioned the lack of intelligent animals that fit the bill, there is no reason an alien crab like organism could not have intelligence. $\endgroup$
    – John
    Commented Dec 29, 2016 at 17:54

To have technological civilization, at the very least you need to have tool usage.

Octopuses have been found to use tools with their very dexterous arms.

You also need a large brain and if they are to be able to survive on land for some period of time that seems to suggest a mammal.

So a mammal with large head and a few dexterous arms which can be used for swimming and walking on land as well as tool usage.

Sensory wise, if they are primarily oceanic species, sonar seems plausible.

Obviously, living in liquid they'll be very streamlined.

Finally, they need to have a social structure, work well in groups, which also seems to suggest a mammal.


I would guess some evolutionary descendant of the Pacific striped octopus. Octopuses are extremely intelligent (especially this kind) and the tentacles allow them to be dexterous. The Pacific striped octopus is also very gregarious which would allow for social groups.

I would guess that in time the octopus's beak would decrease in size along with its muscles allowing more room for its brain much like our jaws are much smaller than our evolutionary ancestors. Overall I think the head size would decrease. The animals would probably take much more time to figure out how to get to space than we did since they would discover fire much later. They as a society would probably be more advanced in architecture as they would have to deal with the strong currents underwater. They would also probably be culturally extremely developed.

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    $\begingroup$ If you use and alien octopi you can give them a more reasonable breeding mechanism which will go a long way to helping them. No more mate once then die. $\endgroup$
    – John
    Commented Dec 29, 2016 at 5:50
  • $\begingroup$ Thanks for the suggestion about the beak decreasing to make room for more brains, and also for the pointer to a species we know about today that isn't anti-social. $\endgroup$ Commented Dec 30, 2016 at 21:35

I think you need to keep in mind, that the land mass and air above water level to those creatures is like space to us. So the question: "What could be up there?" would firstly mean the air. So their first attempts would be, to enable themselves to either walk on land or fly in the air.

(Nonetheless, they would need a motivation to do so much before the end conflict leading to leaving for space.)

From that point on they would start making better tools, and those tools which enable them to leave water will a) enhance tool production b) produce some kind of industrie c)enable use of other materials found "up there" and finally d) enable to think about what could be above "up there"...

For sea creatures I would guess the first thought about leaving water would be to mimikry those who can, like crabs. So they might start developing a kind of artificial exoskeleton unless they have techniques of DNA altering.

This exoskeleton which certainly will be quite improved over time and could be the basis for spaceflight.

Another point is, that additionally to "up there" in their culture there certainly would be the aspect of "down there" as they won't be able to travel far down without environmental suites either. This could even enable higher industry (using volcanos - see my addition to fuzzys post).

  • $\begingroup$ I just saw your edit in the review queue and as it's not easy to see the feedback people give on those (you have to go to your profile and click on the edit suggestion) I want to write this here as a comment: edits should not add details; that's up to the author. If you have a new idea that was inspired by a different answer you should write a new answer and refer to the inspirational source. Or just add the details to this already existing answer of yours. $\endgroup$
    – Secespitus
    Commented May 24, 2017 at 8:40
  • $\begingroup$ Welcome to WorldBuilding by the way! If you have a moment please take the tour and visit the help center to learn more about the site. Have fun! $\endgroup$
    – Secespitus
    Commented May 24, 2017 at 8:43

Inspired by fuzzys approach I made some thoughts regarding possible underwater skills, tools, etc.:


  • Many already said that remnants of hard shelled exosceleton animals or corals can be used as tools (like knives).
  • There are certainly some sea plants to make ropes from. These can be a starting point to make nets or are used as fences against hostile animals.

Skills and Techniques

  • Underwater surgery using those non-metal knives could certainly be possible.
  • Aquacultures (see below)
  • Art (see below)
  • breeding animals to fit their use
  • brain surgery on aggressive animals if taming doesn't work (to be able to direct them)

Farming Plants

  • Growth of Corals can be regulated on purpose for several reasons (like Sponges, Food, Art, Architecture).
  • Seaweed or similar plants to make ropes.

Aquacultures and interactions with animals

  • Using ropes as fences, or a tamed potentially aggressive animal as herding animal, it can produce aquacultures for food, as a kind of underwater zoo, or other purposes
  • aquacultures can be a food basis for bigger tamed working animals
  • they can also be used to culturize and tame more powerful animals
  • shell aquacultures can be used to produce perls and mother-of-perl for art and hard shells as a tool basis

  • As this species is more intelligent than others underwater it can produce similar effects like between humans/wolves/dogs. So there would be at least one other species which developed side by side as a companion like dogs evolving from wolves as some of them outsourced the hunting to the humans concentrating on their remnants for food. Of course this animal would look quite different than the one it evolved from.

  • whales could help moving large objects using a harness of ropes
  • tamed sharks or orcas as protection against aggressive animals


  • Using poisons as a basis for producing medicine
  • use of non-metal scalpells and saws
  • syringes can be made from a coned shaped shell as needle in combination with an air bladder of fish for the medicine and a second shell around the bladder to reduce or enlarge the size of the bladder therefore injecting or taking fluids

Possible ways of leaving water

  • breeding crabs as hosts / living environmental suits for land walks (possibly in combination with surgery)
  • Flying could be possible if the atmosphere has a quite high CO2 atmosphere as that gas is quite heavy. So if they can produce gas which is lighter they can use it to fill a balloon made from whaleskin.
  • They could also try to breed fish like giant sharks to develop a giant air bladder which can be used as a tool or basic material. Maybe they can even try to alter their physiology over time to produce a different gas which is even lighter than CO2.


  • Culturizing corals can be a great way of sculpted living art.
  • Pearls and Mother-of-Pearl can be a elements in decoration (like tools, sculptures, architecture)

Higher Industry and other resources

  • I am not sure about that, but one approach could be to use heat/hot water of underwater volcans.
  • For using them they would also need environmental suits against the high pressure. I am not sure wether they might be developed before or after the environmental suits for land walks or flying?!
  • Mining for certain minerals, gems etc. would also be possible under water, but I am not sure which ones could be of use under water. Maybe in combination whith an underwater volcano industry?!

My approach to this question begins with imagining what sorts of work would need to be done in an underwater environment. What assumptions can be established about these creatures' skills, and what do they lack? What sorts of objects must be associated with their work?

We imagine tools in an air environment as moving in certain ways and modifying or striking objects to change them in certain ways. How does the undersea environment affect movement and interaction of objects? What unique needs will be present underwater that do not exist in the air? How do biological requirements dictate the need for tools? What aspects of 'culture' would develop differently in the underwater environment, or how would what constitutes culture differ?

  • $\begingroup$ Water is much denser and more viscose than air, so hammering or chopping activities, which involve rapid motion would be much harder than in air, probably to the point of infeasibility. On the other hand screw fasteners (if producible) or sawing/cutting via slicing or shearing should still work pretty well. $\endgroup$
    – Catalyst
    Commented Dec 28, 2016 at 19:33
  • $\begingroup$ Exactly - how would you have metallurgy underwater? $\endgroup$ Commented Dec 28, 2016 at 23:34
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    $\begingroup$ Is metallurgy "necessary" for a spices to be considered developed? Cannot they have different method of obtaining advanced tools? Just for example, what if they 'breeded' corals into making shaped nanomaterials from carbon? That would definitely 'match' metal tools of land-dwellers. $\endgroup$ Commented Dec 29, 2016 at 0:26
  • $\begingroup$ @David162795 Minor nitpick, but past tense of 'to breed' is 'bred'. $\endgroup$
    – user
    Commented Dec 29, 2016 at 13:33
  • $\begingroup$ I'm struggling withe the air requirement. Why would they have to get to land. Couldn't you do things with materials other than metals that would possible/feasable underwater. There are chemicals that work and bond underwater. Laquer barnacle glue over coral and hollow it out for the shell of a craft. That's just a spitball idea. $\endgroup$
    – Paul TIKI
    Commented Dec 29, 2016 at 19:38

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