Set in the year 2065 in the underwater world of Marineville, the surface world is united under one government and is at peace. Having conquered the galaxy, man has turned his attention to the exploration of inner space, the oceans that cover three-fifths of the world and provide a vital new source of mineral resources. But this inner sanctum is peopled by many alien races who are hostile to the surface people, whom they see as invaders of their domain. One group, the Aquaphibians, a race of undersea warriors ruled by Titan, have sworn to invade the surface world and destroy the forces of the World Security Patrol, an international organization set up to preserve world peace.