Conducting an inspection of the equipment on the offshore oil platform, one of the workers fell into the sea. His death was inevitable, but was saved by the crew of a small submarine, which happened to be nearby.
The worker was brought to the secret base of AQUATICA - people with implanted shark gills, which allowed them to breathe freely under water. The prisoner was asked to become a member of the underwater fraternity, agreeing to a surgery to transplant the gills. Otherwise, an unenviable fate awaited him - the inhabitants of the ocean needed human plasma.
The prisoner makes the decision to run. Diving equipment is required to get to the submarine and leave the base. Upon discovering an escape attempt, the protection of the aquatics raises the alarm.