I put 2 hours into this.
This isn’t a bachelor thesis, but I’ve put a lot of thought into this. please don’t ban me
Hydrothermal vents. They’ve been suggested to smelt metal, but here’s the deal. A quick google search revealed they heat up at temperatures upwards of 370°C. Copper melts at a temperature of 1085°C, much higher than that of the vents. Of course, these are Earth numbers. For the vents to even be able to melt copper, the ocean would have to be extremely deep to be near the planets core, which will make it much hotter. Of course, the pressure would be enormous, unless the ocean level also descends with the depth of the vents. First theoretical boundary.
After you get hydrothermal vents that are hot enough to melt copper, you need a creature to get it to melt. Well, believe it or not, there are animals that currently live around hydrothermal vents. Giant tube worms, limpids (sea snail), shrimp and clams are some of the animals that live around the vents. That’s because the vents usually spill out a lot of dissolved chemicals, which fuel the microbial life, which in turn fuel the animals. I found out through my research that hyperthermophiles (beings that thrive in high heat) have a cell structure that contains more saturated fatty acids (although a citation was missing, so this may not be 100% accurate), although they were all unicellular. So if a creature like that evolved around a hydrothermal vent, it would be advantageous for it to keep this trait, because of the abundance of nutrients, although the possibility of that is up for discussion. I’m no biologist after all. Second theoretical boundary.
This brings me to my next point: primitive tools. This point actually favours the vents, since they usually form massive exploitable deposits, so, in theory, if a creature could manage to somehow smelt and mold the metal, getting it wouldn’t be a problem. This also means making primitive stone tools wouldn’t necessarily require smelting from the start, as you just need to find a sharp piece of stone to cut down seaweed or coral or sea trees, which you can use for early shelters. Building underwater huts has already been discussed and the general consensus was that it was easy underwater, so I’ll skip over that. Now, you have your tribe of fish people (possibly with high heat-resistant skin, but not confirmed), with basic stone tools, going around prodding other fish to eat instead of using their mouth. This means they also developed some sort of prehension member, which may have evolved from their tail, or their fins (just speculation, underwater creatures aren’t just limited to Earth fish designs), to grab the tools. This means the underwater civilians must have a prehensile member to become a proper society. Third theoretical boundary.
You might wonder, why would they decide to approach the vents to smelt metal? Well, at a stretch, it might be an accidental discovery, like agriculture or Penicillin. A fish might have swam around, found a rock, and decided to chuck it at the vent, and see the rock start bubbling. Curious, it watches the rock, and it sees it slowly melting and dissolving into the water, to cool into tiny mineral deposits. They start experimenting with which rocks melt how quickly, and how to differentiate each rock. Then, they will make crude moulds out of the rocks that take the longest to melt (or don’t melt at all, catching them back when they’re expelled), and suspend them over the vent, around the area where the metal starts cooling, so that they can force the metal into constant contact with the vent, eventually melting, wherein they will remove the mould from the area and cover the metal so it may cool into the piece, their first man-made shape. Why would they do that? Well, why did we start melting rocks and then moulding them? Experimentation and curiosity. We saw that different metals were good at different things, so through testing, we melted the metals into specific shapes. So, metallurgy would have to be accidental at best. Fourth theoretical boundary.
OK, you melted metal and advanced a lot. How will you industrialise? We had lots of coal-powered steam machines, but fire won’t work underwater. That’s where currents come in. It’s like a water mill, except it’s more accessible and less constraint to location. They can just build propeller that will turn the machine. Simple, renewable and clean. If you don’t like that solution, back to the vents. The water is already boiling, you just need a means for the current to evacuate once the piston is pushed up, and give it enough time to come back down before the next wave. Of course, industrialisation occurs, factories everywhere, population explosion due to better living conditions, and no coal mines! What’s missing? Electricity. Unfortunately, being underwater means there’s no wiring possible without endangering everyone swimming around, unless you insulate everything from the beginning. Assuming the fish discover electricity (maybe through a deadly experiment), how would they generate it? Back to the propellers. Using an alternator, they can transform the kinetic energy generated by the water turbine into electric energy, giving electricity to everyone!
You have the power of electricity at your fingertips, but what’s next? Land! You need to develop land colonisation before thinking about space. Why? Resources will probably start running low by now, and land is still fresh and full of resources. You build a pressure suit for your colonisers, and you build a land vehicle to get you from water to land, and you start colonising. Once you’ve mastered land, pressure suits will be useful for the next frontier: SPACE. Since you can establish infrastructure on land, you can start populating it, building mainly with giant construction vehicles to do the heavy lifting for the Giant walls encasing the city to get pumped full of water for the inhabitants. Then, you’ll build a rocket platform, and rocket into space.
In conclusion, I think I gave fair points in regard to some glaring plot holes of founding an underwater civilisation (tell me if I missed some). I breezed through the whole industrial-space part, because I was getting kind of bored and no one discussed it, so I ran out of ideas. My verdict: It’s possible, but highly convoluted and too reliant on specific events to be common. In your entire playthrough, I don’t know if you could ever find an auto-evo underwater civ, because it’s just so much easier on land.
What are your thoughts? Did I get anything wrong? Do you have anything to add? Do you want to fight me IRL?