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I remember reading an anthology/collection of sci/fi and fantasy stories sometime between 1990-1996 which had as its first(?) story one called 'Kraken' or 'The Kraken' maybe.
It was about a post apocalyptic water world where the only surviving people were living on floating islands of junk and seaweed. The most interesting theme to me was that the protagonist rediscovered ways of resynthesising metals and chemicals from the sea and the sun using crude chemistry principles.