Have you ever defended under-sea canal, or a tube? No? Now you can experience it. Fighting is done by creative gear. Use electro-ray, various cannons and laser beams, everything you can imagine. The weapons have different costs. You can get cheapest for fifty credits and the most expensive are about four hundreds and more. The tube is heavily branched, so it is easy to find a strategic position for a gun. When ready press The Next Wave button and observe. It is possible to add more weapons during the game, so you can always manage a difficult situation.