Captain your submarine through dangerous waters to reach the enemy port then destroy their cargo ship in this three stage game.
In stage one, you have to manouver your submarine through the obstacles and mines to reach the right end of the screen.
In stage two, you have to shoot down a number of enemy planes. An enemy ship is also attacking you: if it's above you, it will drop bombs. If you come up to the surface it will fire torpedos. You can only shoot the ship sideways (not upwards). You can only shoot the planes from the surface, by pressing fire + up. If your sub is on the surface, and the plane is above you, it will drop a very fast.
In stage three, you have to sink the mother ship. No one is shooting at you, and you can only move left and right. Once you fire your torpedo, you can still adjust its course by moving left or right. Once the mother ship is sunk, you go back to stage 1.