There are two dominant species on the planet Someplace. One is humanoid, much like us. They have modern-day technology, and have similar physical traits. There are around 1 million people in the military who actually fight. Military distribution is like the US military.

However, the other species is a sea-dwelling species, with similar technology, but adapted to water. They have some way to grab things (think webbed hands or feet). They cannot survive on land, needing moisture for their skin (gills?) and can only breathe in water. They have a similar size to the humanoids, and have a similar number of military personnel. They do have a limited "air force", with planes filled with water tanks, and such. They have a lot of boats filled with water.

Spies and intelligence don't exist, because the two species look quite different. They can communicate, but they speak different native languages.

So, my question is, could the sea-dwelling species attack the land beings, and possibly win? If so, how could they win? If not, are there any modifications you could make to the sea-dwellers to give them a chance to win?

Edit: I know there's a similar question, but it's about humans attacking sea creatures, not the other way around.

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    $\begingroup$ if you fill a boat with water, it sinks. Boats only swim because they don't have water in them... $\endgroup$
    – dot_Sp0T
    Feb 24, 2018 at 19:48
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    $\begingroup$ Your question reminds me of the movie Orca. You may want to watch it; purely, of course, as research. $\endgroup$
    – user
    Feb 24, 2018 at 20:36
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    $\begingroup$ How do they build vehicles/develop technology when they can't possibly smelt metal underwater? That, right there, means they will never develop computing devices, or guns, etc. Heat/fire is also a necessity for many other purposes having to do with chemical processes, and - essentially - the advancement of civilization. $\endgroup$
    – AndreiROM
    Feb 24, 2018 at 22:10
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    $\begingroup$ I know this is flippant, but frankly... poison the sushi. The sea produces an enormous quantity of food, and one would think your sea-dwelling creatures could control that. $\endgroup$
    – JBH
    Feb 25, 2018 at 0:31
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    $\begingroup$ @AndreiROM, you're right, of course, but it's worth cross-linking this question with technology - how would an aquatic civilisation forge tools?. $\endgroup$
    – JBH
    Feb 25, 2018 at 0:37

3 Answers 3



If this nation is similar to the USA, then they will be heavily dependant on exports, specially oil.

So, all that this species need to do is raid the sea lanes and stop any commerce, let the humanoid nation slowly starve for oil or other resources it would need from the outside.

When the humanoid War machine has grinded to a halt, the marine creatures can step in and demand their total surrender.


If the humans are all centered in a single landmass with no maritime trade route:


Humans would still settle their cities near water sources for praticity.

Be it the food sources of the oceans or the water source of the rivers, the oceanic creatures could find a way to sneak in and cause chaos.

Keeping a constant watch over all the coastal areas and rivers would be a dauting task.


The humans are still surrounded by water from all sides, the oceanic creatures would be able to deploy fast strikes against unprotected targets, chipping away the human's defenses and depleting their resources.

Naval Superiority

The humans would have little incentive to develop any kind of serious naval technology, this would allow the Oceanic creatures to use their missile submarines to keep a constant barrage of death over the human's cities. Even with a sizeable airforce, it would be incredible hard to locate and attack the submarines, specially since the humans probably wouldn't have sonar technology.

Economic War

So, some annoying human party is saying things that annoy the fish-people? Well, so it's time to start some considerable donations to their rival party.

Having the technology and the biology to live underwater would give them access to considerable deposits of ores, oil, food, and cheap energy sources.

Even if they are in a state of total warfare, they probably could find some people interested in settling peace in terms favorable to the fish-people in exchange for a few tons of gold.

  • $\begingroup$ This method also forces humans to fight on the sea-dwelling species turf, giving them an intrinsic advantage in the conflict. The humans either have to fight to preserve water-based economic trade routes (which account for 90% of trade on earth) or be economically crushed. Either way they are forced into a tactical lose-lose scenario. $\endgroup$
    – TKOW
    Feb 24, 2018 at 21:07
  • $\begingroup$ Good idea. However, how would this work if the humanoids were concentrated on one continent? Just curious. $\endgroup$
    – Hazard
    Feb 25, 2018 at 1:14
  • $\begingroup$ Edited my comment to answer this situation. $\endgroup$
    – Sasha
    Feb 25, 2018 at 4:49

I could think of multiple ways that your sea creatures could attack land dwelling humanoids assuming they have the same level of technology.

If they are capable of building functional vehicles as described then they obviously would have reasonably efficient ways to mine materials and create large constructs. One idea would of course be for them to build water filled weaponized mechs, but this would most likely be far to expensive to do for the entire military force, and only worthwhile if the mechs were extremely overpowered and capable of taking out large amounts of enemies at a time. Other vehicles, like planes or amphibious tanks, might have a better chance.

A much more effective strategy might be to use ranged weapons capable of being launched underwater, perhaps even nuclear missiles is your species can create them. However if that were the case than the humanoids could likely use the same method against them. Either way the war would be over quite quickly.

The sea creatures would obviously have a huge advantage underwater. If they waited for the humanoids to attack them, which would probably require the use of submersibles, the sea creatures would have a pretty good chance of winning. This might be the most effective strategy for them to win.

Overall if the sea creatures are attacked by the humanoids then fighting them underwater would most likely be the best solution. On the other hand, if the sea creatures are attacking, ranged weapons would probably be the way to go. Either way, with the same tech as the humanoids they should have a decent chance.


So, my question is, could the sea-dwelling species attack the land beings, and possibly win?

This depends on what "win" means. With a surprise attack an inferior enemy can win a battle. I can suckerpunch some huge dude and then kick his head when he is down and then run away with his hat. I win!

Then a war - what is it to win a war? Most human wars are not fought with the objective of exterminating the other side. Human wars are either wars of conquest or political disputes. The merfolk have no use for dry land so it must be a political dispute.

What kind of political disputes might arise between merfolk and drylanders?

  • The drylanders are fishing where they should not and they will not quit. The merfolk attack the boats of the fishermen and then of merchant mariners and then of the navy ships. The drylanders do not see it worth their blood and treasure to keep fighting over some fishing grounds. The drylanders sue for peace, agreeing to give up the fishing grounds in exchange for cessation of hostilities. The merfolk win.

  • The merfolk make periodic raids on human settlements, because they crave liquor and sugar. These raids are destructive. The humans make punitive strikes to dissuade them. It is politically expedient for the merfolk leaders to rally around the cause, and the merfolk make a disproportionate military response, slaughtering an entire human village. The human leaders are concerned about this sort of ferocity as it suggests the merfolk may not be entirely rational. The humans sue for peace, promising a periodic tribute of liquor and sweets (and by doing so, open lines of communication with the merfolk). The merfolk win.

  • The merfolk are well and truly pissed at a country of land-dwellers who will not leave the mermaids alone. They wait until the weather is dry and then emerge in force and conduct a Chevauchée through the farmlands using that fascinating and land-specific weapon of mass destruction, fire. Eventually the merfolk raiders are driven back into the ocean but the agricultural basis of the country has been crippled. These land-dwellers turn to their neighbors for help but their neighbors do not like them any better than the merfolks do. In the early spring the land dwellers numbers are depleted by famine and many have left as refugees. When the merfolk come back to finish the job the remaining military flee. The merfolk win.

  • $\begingroup$ Winning in this case would be capturing the humanoids and enslaving them, forcing them to labor in the mines on land where the merfolk cannot go, and similar grueling tasks. $\endgroup$
    – Hazard
    Feb 25, 2018 at 1:17

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