According to the FAQ page the thing preventing an underwater industrial civilization from existing is the inability to do any metalworking. This is probably because it is hard to start a fire while underwater.
I decided to do a bit of research, because I was bored, and I also want a fish empire.
at first I thought of hydrothermal vents, but the elements they can melt are either radioactive or too soft.
I also came up with the idea of evolving ridiculously long arms to reach onto the beach, but I think it’s a little silly.
Eventually, I thought of the Mid Atlantic Ridge, the ridge in the Mid Atlantic. This made me think of volcanoes, and I decided that volcanoes are fairly toasty, so they might work.
On Earth, deep sea volcanoes can reach 1250 degrees Celsius.
iron melts at 1535, which means it won’t melt, but it would likely be enough to soften it enough to hammer it with a rock.
you could theoretically make a furnace out of rocks that won’t melt.
chromite for example, is fairly common, and has a melting point between 1857 degrees Celsius, which is probably more than 1250.
with this furnace, you could probably make iron tools, or even basic machinery like gears, as long as they aren’t too small.
electricity might be difficult, because water is ever so slightly conductive.
this means we need to insulate the device if we want anyone to be able to go anywhere near it without getting fried.
rubber isn’t the only insulator, but it’s a very good one, so that’s what I will use for my example.
rubber comes from extracting latex from certain trees.
it also goes through a heat treatment process, which you might be able to do in a hydrothermal vent or a volcano.
it is possible that an organism capable of creating a similar substance could evolve on the same planet.
as for the space stage, rockets can be launched from underwater, it is just a slight pain in the rear, because of the increased fuel costs due to the increased drag from the water.
Is this idea worth considering or stupider than it seemed to me when I thought of it?
here are my 2 most important sources, because apparently, new users can only post 2 links(I tried to post 5). feel free to check them out and correct me if i missed anything somehow