Silverberg Robert. The Face of the Waters

Bantam Books, 1991. — 436 p. — ISBN: 0-553-29907-7.The Face of the Waters takes place deep in the future, on a penal colony, inhabited by convicts and their progeny. The planet is Hydros, an ocean planet whose inhabitants live on artificial floating islands.
After a human offense against the natives of Hydros, the human population of the island of Sorve are ordered to leave. Forbidden on all other islands, in a flotilla of ships they seek the semi-mythical island of the Face of the Waters. During their journey they are forced to learn more about themselves, leading to questions about both religion and the purpose of Man. At the end of the novel Robert Silverberg addresses what it means to be human.