Three young couples carrying Ј200,000 of drugs to Morocco are marooned on the North Sea when their boat explodes. They end up on a Brinkstone oil rig, but there is no drilling equipment and no crew. They soon discover the place is a secret genetic laboratory set up because Lloyd J Brinkstone, the billionaire owner of the oil rig wanted to give something back to the world. He firmly believes that the world will end in nuclear fire, and thus hired a team of microbiologists to develop a gene that would enable man to adapt instantly to his new environment. Needless to say, it all doesn't work as expected and it all ends up with a genetically altered shark who wanders about eating people, absorbing their personalities and imitating their physical appearances. Gradually the six get whittled down and the beast designed to be invulnerable seems to be just that