"In Larry Niven & Ed Lerner's "Fleet of Worlds" the human scouts discover an ice-bound ocean-world in which the sapients combine their brain-power to form huge natural computers that can simulate what the outcome of their experiments might be, thus they're able to rapidly industrialise once they emerge on to the surface and start building air-filled laboratories. Forging tools from meteoritic metal might be possible via volcanic vents but fire itself - as a concentrated energetic chemical reaction - could be hard to achieve underwater. Some things do burn in oxygenated water, or even in reaction with water, but how do you isolate the pure components to start with?"

How about make H2, put in a dome. In Hydrogen environment and heat from volcanic vent you will get pure metals.

With relatively low voltage you can get from sea water could split water into H2 and O2