Submarine warfare in deep sea!

You are ordered to drive a submarine into deep sea to destroy enemies.
In mysterious deep sea, your enemies will not only be human beings.
Be a brave man when you see giant octupus and aggressive sharks.
Launch missles to destroy enemies one by one.

Tips:
-Steer on left. Shoot on right. Pay attention to enemies.
-When your enemy is powerful, remember to use different torpedoes and upgrade your submarine in time.