The Last Line Before the Edge of the World

The ocean has an edge, an endless stretch of calamitous waterfalls plunging into the abyss. Slowly, all life on the sea is drawn towards the edge with the ebbing of the tide.   To avoid falling into the void, buildings are constructed so they can move, and most float on the water. There are cities built on the edge, using the flow of the water to power themselves, but which must constantly make repairs to avoid their deep supports buckling under the strain, and interventions made to prevent islands being dragged into them