A dangerous situation has occurred at the Mana One submarine station while on a mission to explore a deeper section of the Mariana Trench, which was conceived by a thermocline. The submersible was attacked by an unknown creature, which left the three crew-members stranded. A few hours afterwards, Mac, Dr. Heller, and Jiuming and Dolly Swim's in the Ocean as they all..venture to Thailand to recruit an old friend, Jonas Taylor, and ask him for help.

He eventually agrees and you all arrive back at the Mana One. The situation has gotten worse by the creature escaping the thermocline, and with Jonas’s help, has been determined that it is a Megalodon. So you and the rest of the crew have put a tracking device on it, and are brainstorming how to kill it. During this time, Mac has been particularly concerned about Dolly being involved, since he doesn’t want Dolly to get hurt or worse.