After a nuclear war, Earth's population is mostly wiped out. The survivors have build eight underwater colonies - that's all what left from humanity. Unfortunately, the nuclear war was just the beginning. An alien race, the Spurcians, made advantage from this situation. So they've conquered Earth and have taken those eight cities. Now the only survivors are inside the freight vessel Genesite, which is in orbit. On a last attempt to free the underwater colonies, the pilot Josh Aldrin (you) is send back. Meanwhile, the Spurcians destroyed the freight vessel, making you the last human on Earth. So, you are now on revenge...
Your job is now to flight with your craft above the water surface. Destroying enemy alien crafts and energy generators. When you destroyed enough generators, the energy shield from the main pyramid fails, and you can attack the level guardian. Once he is destroyed, you use the tunnel, which connects the underwater colonies, to get to the next one. You will play all eight colonies. While in the tunnel, you have the chance to collect power-ups to regenerate your ships energy (health). Inside a level, you have to live with the energy you currently have. Oh, and by the way, you have, like in reality, only a single life.