From publisher blurb:
The Grand Stair stretches behind the scenes of the multiverse,
The Doors upon its unfathomably vast span leading the way to gossamer worlds of limitless variety and infinite possibility. Many worlds have oceans, but in this reality a tide is rising that will soon claim all.
Poseidon's Rapture was once a world where land and sea existed side by side in harmony, but when the great all-father Poseidon vanished, something went wrong. For three hundred years the water has been rising, swallowing cities and continents, forcing mankind onto desperate ships of survival and reducing the tallest mountains to small – and shrinking – islands. In this flooded realm the future belongs to those who have mastered the sea, sailing upon it and diving beneath it. It is a realm of ships and submarines, scavengers and scoundrels, swashbucklers and sea monsters. Open the Door, and get ready to swim.