Sub-Mariner (Sub-Mariner #5)

After the events of last issue, a disorientated Namor finds himself on an isolated island where he is attacked by a giant robot. Namor destroys his foe but the robot explodes and Namor is knocked unconscious. A couple of men appear and take the Atlantean prisoner. When he awakes Namor is inside a strange base surrounded by shark tanks and is clothed in a metallic vest. A woman named Diane Arlis appears and explains Namor has been taken prisoner by Dr. Dorcas who appears and using a button on his belt releases electric shocks from Namor's vest, proving that he is in control. Diane explains her brother is a former Olympic swimmer who due to an accident is unable to swim anymore.

Todd Arlis has paid to be part of Dorcas' experiments with sharks in order to be able to swim again but since they captured Namor, the Atlantean will be used instead of sharks.The experiment goes wrong when Dorcas uses too much power and uses both Namor and the sharks to send power to Todd. This turns Todd into a mutated human/shark hybrid who takes the name of Tiger Shark. Tiger Shark destroys Dorcas' machines thus accidentally freeing Namor. The prince attempts to stop this new villain who is his equal in strength but Tiger Shark stumbles upon Lady Dorma whom he takes hostage.