It is the future, and the world is getting smaller by the second. As a result of the machinations of the rogue scientist Zorndyke, all land at sea level has begun to succumb to the expanding ocean tides. Billions have died, and mankind is now at war with Zorndyke's army of water dwelling hybrids. Mankind's last hope lies within an international fleet of submarines and the vessel, Blue Submarine No. 6, and the pilots: Kino and Hayami.