AquaNox

Aquanox is an action shooter that takes place in the future where all the world population lives underwater. Are you a member of a special underwater commando whose members already became a war heroes in a previous war. Your current task is to find and neutralize war criminals. Fighting in the underwater world is not simple, in your various missions, you will encounter the rebels, pirates and even mutants.
The story has a very extensive background and the game itself will introduce you to a wonderful underwater world. With wonderful graphics, even by nowadays standards, everything has been made to make you feel how an underwater life would be, including floating seaweed, outstanding lighting effects and explanations about the scientific terms you will encounter in the game.