A submarine was kidnapped and you as the Submarine captain have to rescue yourself and your crew from this labyrinth full of enemies. Enemy submarines and battle boats make it pretty hard and without refreshing your lives and torpedo munitions you will not get far.
Your submarine is very fragile and you are loosing lives even by the smallest contact with your surroundings. The enemy battle units and their torpedoes will not let you out from the labyrinth without fighting but your submarine is much more agile, has two speed levels and it can defend itself with torpedoes, too. But their amount is limited and without shooting at barrels spread all over the level you will soon be out of munitions. But be alert, some of barrels can contain unpleasant surprises. You can only escape if you collect keys to open automatic doors and if you act smart and fire your torpedoes faster and more accurate then your opponents do, without losing the control, colliding and loose worth full lives. The enemy submarines shoot horizontally in both directions and battle boats can shoot down additionally.