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87

You can see octopodes crawl out of a tide pool and into a neighboring pool with little difficulty. octopodes have been known to crawl out of a tank in an aquarium and have the crab in the tank next door for dinner. They have even been known to shut off lights that bother them in their tank at an aquarium. They have been documented crawling out of their tanks,...


86

My question is, would it be physically possible to do that with the air tank? No. Source: Tried it. We've actually been taught to breathe off a tank without a regulator. You can do so by feathering the valve. But even when you fully open it, the thrust is simply not enough to propel you at a speed comparable with even relaxed finning. Much worse than ...


83

Instead of electronics they could develop fluidics: http://en.wikipedia.org/wiki/Fluidics We've built fluidics logic circuits to control ICBM's and rockets and nuclear reactors - basically environments that are harsh/destructive to electronics. But we sort of stopped developing fluidics further as hardening process and redundancy algorithms improved to the ...


77

One word: fire. Cooking and metalworking are the first two things that pop into my mind that are made easier, if not possible, on land. While you could argue that neither is necessary for an aquatic species, neither is necessary for terrestrial species either, but have certainly benefited the human race.


75

Octopodes are not going to colonize land the same way we've colonized space - they're going to colonize the land the way we've colonized the sea. Penguino has done a pretty good of addressing how different it is for humans to go to space versus octopodes coming ashore. But there is a parallel that's much closer to shore (so to speak). An octopus' ability ...


58

Physically there are no hard limits as the weight problems are solved by buoyancy. You would end up with interesting internal systems to handle things like respiration, blood flow, etc but solutions can be proposed for all of those. The immediate problems that are going to prove limiting factors though are: Mobility Only the outer surface of the creature ...


56

Technology could develop, arguably would automatically, if aquatic creatures reached a certain brain size. but.. The first major impediment to the formation of technology underwater is the lack of oxygen. Water in general is not an efficient solvent of oxygen for example, a human would need gills several times their body area IIRC something over 15 square ...


54

Here is a way to bypass the issue Our hero removes his air tank, points it away from himself and starts fumbling to undo the top. It's not working! He's never opened one of these things himself let alone underwater, let alone uninstructed first time around while being attacked by a shark, and these things probably have safety mechanisms to prevent stupid ...


51

Give that Columbus' craft were built using Carvel construction (butt jointed wood caulked with tarred hemp that is hammered into the joints and then a coat of tar over everything beneath the waterline), and given that we have already found oil-eating microbes to exist.... imagine hitting a massive, dense plankton field saturated with hungry microbes in the ...


51

Probably, but it depends on a couple of things Firstly: The weight of the loads they're trying to move. If they only ever move things that can be easily pulled into the open water there is no reason to invent the wheel. Even if the loads are a little too heavy the use of 'buoyant' objects will let you get away without wheels. If, however, you're talking ...


51

What you described is an old invention:the wax tablet. Spermaceti from sperm whales is just one of many waxes your underwater people could use. Some of the fishes also contain significant quantities of wax. If you need only a short-term solution, animal fat would also do the job. I couldn't find any seaweed that secretes waxes, so I hope your underwater ...


47

Awesome! I can talk about what I think is one of the coolest inventions of all time: the analog computer. An analog (more properly, a mechanical) computer was actually the world's first "computer" - the Antikythera Mechanism. It was an ancient Greek device that predicted the motions of the planets and other astronomical objects. Only parts of it have been ...


45

Don't take it personally, but if you think computers are only made of silicon, you must have sand for brains! The first computational apparatus, primitive neural systems evolved in an aquatic environment. For 1.5 million years (or so) they have developed environments that protect them from electrical and mechanical failure due to dehydration. These systems ...


45

Bubble curtain. https://www.eurotrib.com/comments/2012/9/6/165418/5127/3 Depicted - an oil rig with a circumferential bubble curtain to reduce underwater noise. https://en.wikipedia.org/wiki/Bubble_curtain A bubble curtain is a system that produces bubbles in a deliberate arrangement in water. It is also called pneumatic barrier. The technique ...


40

Mermaids perform surgery like this: The patient is laid out on a table with the body part to be operated on at the highest point. A transparent sea shell is then lowered over the target area. Clean air, brought from the surface in shells, is released under the shell until the entire area is "dry". This prevents the blood from clouding the water above the ...


36

You would die quite instantly. L.Dutch's answer is accurate if you do the shift on a reasonably short timescale. But if you do it really fast, which I'm getting the impression is your goal, the story is a bit worse. It is true that most of the body is solid or liquid, and thus basically non-compressible. Only the air volumes will be squished. However, ...


35

Until the pressure causes the water to no longer be fluid. Planets can (theoretically) be made of nothing but water. Although after a few hundred kilometers, the water in the center may be turned into some exotic version of ice due to the pressure, so one would not be able to "dive through" the planet, and thus the ocean would have a limited depth. ...


34

Binary Consider how complex a computer is and what it is capable of, yet all its code is composed of almost the most rudimentary elements possible: zeros and ones (binary code). So, the computer software you and I are using right now to communicate is being transmitted to each other via binary and all languages the human race has ever developed have also ...


33

There are a few issues that need to be considered separately: Constructing water-filled environments for a water-breather to reside in on land isn't a significant technical issue. The manufacturing requirements for a salt water pool or aquarium are far simpler to achieve than for an air-filled canister to be used in a vacuum. Getting onto land from the sea ...


33

A bubble curtain is a decent idea, but for something more static, that doesn't require continuous power... A sponge wall. You want a series of baffles that will allow water to pass through, but will choke and disorganize the flow, absorbing and dissipating shockwaves. Sponges will do that just as well in water as spongy materials do in air to absorb sound. ...


32

Marine watchdogs. First option: Build a net wall around the city in the water like torpedo nets. Inside the net give a cautious and jumpy sea dweller a home. The net has no warning function, it simply isolates the sea dwellers from predators so that they are moving freely around the net. If something is inside their waters, the sea dwellers are fleeing ...


31

Fishpedo You want stealth. Then be stealthy. Blend in. The ocean is full of fish. Look like a fish. Move like a fish. Have the sonar profile of... you get it. The sub cannot destroy every medium sized fish that comes into the vicinity. Have it swim around lazily in a fishlike matter. Then it gets close and BLAM! The Mossad shark depicted here has a ...


31

Domesticated Molluscs Giant clams are just one sort of shellfish, but there are potentially many others of various shapes and sizes. You don't even need to grow clams this big so long as you are content using lots of little shells in your building. In particular, I'm thinking of extinct Rudist bivalves that came in a dizzying array of shapes and sizes and ...


31

You can have tectonic plates even on a water world, that is still "land" under there, you just have enough water to cover it all. In your case, any tectonic plates carrying enough land to break through water are all adjacent to each other; just like our continents were once all adjacent. Look at early Earth and Pangaea for an example. With multiple plates ...


30

Basically everything that you thrust. The issue with underwater combat is, as you mention yourself, the drag. Thus every weapon that relies on swinging or other movement in order to abuse its weight to make it hit harder will be at a disadvantage due to it being harder to move it against the water. Everything you thrust straight forward though will be very ...


30

Well, I think the city founders should maybe respect the Dutch a little bit more, because they don't know what they're getting into. First and foremost, salt water is incredibly corrosive. There's no good way to protect your buildings from it, and any solution will require constant maintenance over time. A lot of resources and manpower are going to go into ...


29

First of all, holding your breath while emerging from a deep dive is a really bad idea: the air in your lungs will expand as you approach the surface and will turn you into a balloon, probably killing you faster than gaseous embolism would do.* Then, coming to your real question, to get propulsion from a rocket in air we use a Venturi tube to accelerate the ...


27

This Answer by TechZen gives a lot of insight into the technology of an underwater civilization. Specific to your question: Tools underwater would be much different than we think of them. For example, swinging a lever like an hammer or axe, is not efficient under water because water resistance robs all the energy. Plus, rapid high energy motions stir up ...


26

Braids of seaweed. The ancient Inca used knotted fibers, or quipu, to record events and information. With enough effort, seaweed could be manipulated (slicing then braiding) into thin cords, which could then function in a similar way as quipu. I wouldn't be sure about the lifespan of these cords -- it depends on the manufacturing process -- but these ...


25

Kraken Can't drop depth charges if your ships have been eaten.


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