Why do we even need underwater smelting as underwater creatures? I am sure you can make a floating platform and either hold breath ( How To - What Fish Can Survive the Longest Out of Water? | Live Science Forums ) or just make reverse scuba diving (strap some wooden buckets with water to your gills, its not that hard lol). Then you can just make a furnace! It would take a long time to discover that there are things you can do above water you can’t below water, but it would be possible! Now prove me wrong… (I am reviving this topic since it is the only one unlocked about underwater civilizations and I didn’t want to make another topic)