It's at the bottom left of the screen. If you know where to collect steam( base of the lava flow into the water, below where you collect the lava) to the left of that, there is a cliff at the bottom left corner of the screen, near where they fish. I was only able to get it with a Master Gatherer. It will say that villager is interested in the salty water.
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From the Darkness she comes, the light shows no form, yet tranquility proceeds, the accursed Storm...