Featuring the first appearance of Black Manta! When Black Manta captures Aquaman, Ocean Master decides that nobody but him should defeat Aquaman and attacks Black Manta--all with Aquababy caught in the middle!
A strange submersible vessel descends on Atlantis, then begins circling the domed city. Upon investigation of the craft, Aquaman is beset by the manta men, horrific mutated minions of the Black Manta. The bio-magnetic hull of the Black Manta's drone submarine holds Aquaman fast to the outer hatch. Immobilized, he is a stationary target for the manta men's stun rays. With Aquaman thus occupied, Black Manta releases his ship's umbilical cable, which latches onto the Atlantean dome. Seeing Aquaman imperiled, Mera and Aqualad depart Atlantis to mount a rescue.. Using his body as a counter weight, Aquaman keeps the drone ship rotating at a rapid enough speed that the manta men are unable to get a bead on him. Mera destroys the drone ship with a hard water constructed hammer. The umbilical from the Black Manta's submarine begins emitting light particles that permeate the Atlantean dome. The ocean water within the dome begins to boil. The Atlanteans drain the dome, thwarting whatever plan the Black Manta has initiated. The Atlanteans, however, can only breathe oxygen for one hour. At best, they have only delayed whatever inevitable fate the Black Manta has planned for them.
With the manta men hot on their trail, Aquaman, Mera, and Aqualad return to Atlantis. Once inside the gates, a defensive force field is activated which repels the manta men. Aquaman orders the dome be refilled with water, before the Atlantean populace suffocates. As the pumps fills the dome, the ocean water, once again, begins to boil. The light beam Black Manta focused on the Atlantean dome has molecularly infused it with a chemical compound that causes the sea to burn. Vulko, the chief scientist of Atlantis can see no way to reverse the effect. Aquaman initiates "Project X". A serum is administered to the Atlantean populace that allows their lungs to adapt to breathing air. Only Aquaman, Mera, their infant son, and Aqualad are spared the inoculations, so that they may continue to protect not just Atlantis, but the seas as well. His scheme thwarted, the Black Manta departs Atlantis. Aquaman and Aqualad head out on patrol, to search the vicinity for the Black Manta. With the two heroes out of Atlantis, the Black Manta returns. After a short skirmish with Queen Mera, that leaves the Atlantean monarch unconscious, the Black Manta abducts her infant son, Arthur, Jr. The Black Manta issues an ultimatum... Aquaman's life for his son's. As Aquaman prepares to surrender himself to the Black Manta, another submersible craft descends on Atlantis. It is the hammerhead shark shaped ship of the Ocean Master.
An unbreakable glass cone, attached to the Black Manta's ship by an umbilical cable, is lowered over Aquaman. As the Sea King is drawn up towards the Black Manta's submersible, Arthur, Jr. is released, traveling within a capsule that is launched at Atlantis. The capsule, however, turns back towards the Black Manta's vessel. It's a double cross. Before the capsule can reach the Black Manta's submersible, it is intercepted by a grappling hook, and pulled into the Ocean Master's ship. Enraged at the Ocean Master's interference, the Black Manta fires on Ocean Master's ship. The two ocean going marauders engage in an undersea dogfight, with Aquaman helplessly caught in the middle. Ocean Master collapses a coral outcropping above the Black Manta's craft. The vessel sustains massive damage. His ship destroyed, the Black Manta is, nonetheless, able to launch one final torpedo that decimates the Ocean Master's ship. Aquaman summons two sperm whales, instructing them to ram the glass capsule imprisoning him, until it shatters. With Ocean Master laid out unconscious on the sea floor, the Black Manta commands his manta men to finish him. Arthur, Jr., however, uses his inherited ability to create hard water constructs to defend the Ocean Master. Aquaman attacks the Black Manta. Just as the Black Manta gains the advantage over Aquaman, a revived Ocean Master attacks the Black Manta. The two villains, locked in mortal combat, are swept away by a powerful ocean current. Terribly injured, Aquaman scours the sea floor for his infant son, but, after several moments, collapses into unconsciousness. It is the Ocean Master that finds the infant heir to the throne. In a rare moment of humanity, the Ocean Master return Arthur, Jr. to his father, though still vowing to slay Aquaman on their next meeting. Aquaman and Arthur, Jr. reunite with Mera and Aqualad, while, once again, the Ocean Master escapes into the ocean's depths.