Aquaman is the supporting character in the TV series, Justice League. He made his debut in Superman: The Animated Series. He is the King of the undersea realm of Atlantis and a member of the Justice League.
He was voiced by the late Miguel Ferrer in Superman: The Animated Series and by Scott Rummell in Justice League and Justice League: Unlimited.
Superman: The Animated Series
For years, Aquaman was considered an urban legend, until he was kidnapped and caged by Lex Luthor. He called out, telepathically, to all sea creatures to attack the "surface dwellers." The attack was stopped by Lois Lane, with the help of Superman.
Justice League/Justice League Unlimited
Years later, Aquaman sank the nuclear submarine USS Defiant for intruding into Atlantean territory. When the Justice League responded to the Defiant's distress call, Aquaman allowed the League to rescue the crew on the condition that the vessel be left at the bottom of the ocean. Superman encouraged him to address his concerns to the World Assembly; Aquaman, however, remained skeptical. His military advisers urged him to take the necessary measures and wipe the "surface-dwellers" out from the face of the Earth, but Aquaman instead opted to visit the World Assembly building, and met with the council. There he imposed a peace treaty that would implicate a near-surrender by the surface-dwellers. When his demands were declined, Aquaman stormed out of the World Assembly building, where he was attacked by Deadshot. Aquaman was badly injured, but was promptly saved thanks to the genius of Batman, who provided a special water tank where he recovered. Escaping from the League's custody, Aquaman headed back to Atlantis, only to find his brother, Lord Orm, had usurped his throne.
Aquaman was taken away and shackled to a reef near a volcano together with his son, and Orm sent them plummeting toward the lava. Aquaman managed to break one arm free, but in the face of the imminent death of his infant son, he used his metal belt buckle to sever his own left hand, which he later replaced with a prosthetic harpoon.
After rescuing his son, Aquaman learned that Orm had activated the Doomsday Thermal Reactor, a last-resort weapon Aquaman had built to melt the polar ice caps in case of war with the surface-dwellers. Aquaman set off to disarm it and stop his brother. The two brothers sparred until the ice bridge collapsed. Aquaman ignored his brother's pleas for his life and let him fall into his death. Thereafter, Aquaman pondered about how his own fear for the surface-dwellers put his kingdom and family in peril.
Aquaman attended Superman's funeral. Afterwards, he was a candidate to replace Superman on the Justice League's initial roster. While Lobo claimed the initial spot, only by intrusion and force, the records Superman uncovered in the destroyed Earth's future listed Aquaman as a member. It is safe to assume, then, that had Superman not returned to his present, Aquaman would have become the eighth member.
Later on, Aquaman arrived first to help and save civilians from magma creatures and to prevent an oil spill. He also criticized humans for their stupidity for not considering the possibilities there would be creatures living in the magma chamber they drilled into.
Aquaman dealt with the Ultimen along with Superman, Batman, and Wonder Woman. He faced off against Downpour, who realized far too late that the Atlantean's innate aquatic advantage made him the worst opponent he could face.
He also led an attack against the otherworldly Icthultu. After the Thanagarian invasion, he began working with Dr. Fate. He took a personal investment in the recovery of Hawkgirl, perhaps due to her involvement in the Icthultu conflict. He was also with the Justice League's response to the Dark Heart landing.
In the 2040s, Aquaman's daughter, Aquagirl, had succeeded to his League post. It was also likely that his son has since succeeded him as King of Atlantis after his passing/disappearance.
As an Atlantean, Aquaman was both stronger and tougher than ordinary human beings, and could breathe underwater as well as in the air.
His strength was of the level where he could knock out opponents with just one blow (as demonstrated by how he knocked out John Stewart), break metal chains, and even hold his own against Wonder Woman in a physical fight.
He also seemed to possess superhuman durability, given how his skin was difficult to pierce, and described to be "tougher than a rhino's". However, Superman was still capable of easily knocking him out with just one punch.
Aquaman's most powerful ability was, perhaps, his ability to telepathically communicate with marine life, which enabled him to sense impending threats to his kingdom as well as to summon marine creatures to aid him in battle.
As the King of Atlantis, Aquaman wielded the Trident of Poseidon, which endowed him with great magical powers. It was also possible that his kingly status made him either highly resistant or even immune to water-based attacks, given how Downpour's hydrokinetic attacks left no visible damage on him at all.