The luxury ship Mary mysteriously disappeared while sailing in the Atlantic Ocean, attracting global attention. The Smith Division of the British Metropolitan Police was responsible for investigating the case. During the search, the Lucone rescued three thousand crew members of the Mary. At the same time, they discovered a strange-shaped "iron jellyfish" and received a warning message from it. Later, it was revealed that the crew of the Mary was still alive through a distress message found in the belly of the fish. Dr. Nagaragawa proposed the idea of intelligent superhuman beings existing on the bottom of the Atlantic Ocean, which disagreed with Police Department Smith's pirate ship hypothesis. The crew of the Mary experienced various crises on the ship. They fought against mysterious creatures and tried to find a way out. What is the purpose of "iron jellyfish"? Can the crew of the Marie be rescued?
