The world famous sea explorer, Douglas McKragen, has just discovered five alien pods and disappeared. Now 12 different factions have entered the water in an effort to find out what happened and to take control of the pods. Choose one of the 12 factions and take control of their submarine. Embark on 11 missions in the Story mode and find the truth behind McKragen's disappearance. If the action becomes too much, have a friend help you or challenge him or her to the Battle mode or a deathmatch. Do you have the skills to survive CRITICAL DEPTH?