When Comet Sicara brushed near enough to strip the ozone layer form the Earth's atmosphere, civilization effectively ended - in fact, life on Earth was nearly extinguished. But the underwater cities survived, and some heavily protected land enclaves as well.
When the "ozone summer" years were ending, submarine captain Ron Tregarth rediscovered his lost love, Graciela Navarro. But their triumph against all odds was only the beginning, for the alien known as the Eternal stood between them and threatened to destroy all they held dearest. The Eternal's goal was to absorb the minds of every living thing, to create a death-in-life to enslave the planet.
Frederik George Pohl, Jr. (1919-2013) was an American science fiction writer, editor and fan, with a career spanning over seventy years. From about 1959 until 1969, Pohl edited Galaxy magazine and its sister magazine If, winning the Hugo for if three years in a row. His writing also won him three Hugos and multiple Nebula Awards. He became a Nebula Grand Master in 1993.
Frederik Pohl used these pseudonyms: Edson McCann, Jordan Park, Elton V. Andrews, Paul Fleur, Lee Gregor, Warren F. Howard, Scott Mariner, Ernst Mason, James McCreigh, Dirk Wilson, Donald Stacy and James MacCreigh.
Frederik Pohl. Wikipedia.