The sunken world

A wartime experimental submarine vanishes and, years later, a lone crewman returns claiming survival and the discovery of an advanced submerged civilization. He recounts the vessel's accident, the crew's exploration of unknown depths, encounters with domed cities, temples, strange fauna and technologies, and integration into a society that blends lost science with different morals. The narrative follows expeditions, trials, political and religious judgments, a perilous return journey with demonstrations of engineers and wind-makers, warnings of rising waters, and finally a contested emergence to the surface world that forces reconsideration of progress and the proper use of power.