SWARM: Underwater Metropolis by Vincent Casil

Miranda takes you back to her childhood and what it’s like living in their underwater metropolis, including the significant concerns that only visitors from the past can resolve. Beforehand she and her fellow soldiers share a few meaningful tales of what has influenced most of the colonists deep into the abyss, among them an ancestor of Raymond and Nathan, David’s friends who they never knew, who made a heroic task saving civilizations both sides of the planetary system from above and below the sea. His name was Michael Herron, and just like the three friends, he got lost in the distant future of the SWARM world.