A pirate missile, an invisible submarine and an undersea survey launch Tom Swift Jr. into a new mystery. To work safely in the depths he develops an electronic hydrolung, then sets out to build a sub that sonar cannot detect but that can see its enemies, while frogmen, kidnappers and a propaganda campaign try to stop him.
Cold-War gadget adventure from 1961, the high tide of the Tom Swift Jr. series. Download the free EPUB.