An omnibus edition of Undersea Quest, Undersea Fleet and Undersea City.
When Jim Eden's uncle, the inventor of a valuable undersea device, disappears while testing a new undersea mining process, Eden heads for the undersea mining colony to investigate on his own.
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.