So based on that creation myth, I'd assume that when the Sea Child went onto land, she became the first human. So all of the other humans descended from her. And if "water" is death and "mountains" are life and vice versa, Then I assume our MC— who is basically just in a superposition of dead and alive— is like the reincarnation of the Sea Child, maybe? That's admittedly a bit of a stretch, though.