The setting is a bit dystopian, perhaps… the water people have built a civilisation on the flooded coastal areas of the old world. They gather what they can from the tides and live off the slowly recovering seafood…
Immersive, in the sense that this image is a window into a full world. I feel like stepping through the window into this other reality that you depict, to hear seagulls and the water lapping against the pilings, while boards creak under my feet as I walk along the dock.
You describe the back-story as dystopian, but I don’t really sense that. It might be post-apocalyptic, but there is no evidence that the people are suffering, discontented, or oppressed. Without the façade of high-priced glass+steel+glitter modernity exists a more honest world.
Thank you so very much for your efforts with a detailed and honest answer. And I feel like you, I think. I have added a “perhaps” to my description because I also think that it feels quite good, the life, the environment we are looking into…