Arthur Joseph Curry was delivered prematurely when his mother died of complications. His father did all that he could to save the baby, and injected him with a serum that would allow him to breath underwater. The serum gave him gills, and he can only stay out of water for short periods of time.
During "Infinite Crisis", Arthur was being kept at his home, a laboratory where his father worked. There were storms created by Spectre during his attack on Atlantis and the lab was destroyed, along with the tank that Arthur was kept in. Arthur's father was found dead a year later.
One Year Later
Arthur first appeared in issue 40, of Aquaman (renamed with this issue: Aquaman: Sword of Atlantis). It was marked with the "One Year Later" stamp. It began with Arthur swimming downward, and eventually hearing a voice asking him his name. The voice mistakes him for Aquaman because their first and last names are the same.
The voice directs him to a large battle between King Shark, and many other sea creatures. The voice tells him to help King Shark, and the two of them hold off the sea creatures until more sharks arrive. At this point, King Shark grabs Arthur, and then the voice leads them to a creature known as the, "Dweller In The Depths". It gives Arthur a set of armor that is similar to that of the original Aquaman (orange shirt, green pants), as well as a sword.
Arthur eventually abandons his position shortly before Blackest Night, not being able to take the pressure of carrying on the original Aquaman's position. Tempest succeeds him on the throne for a short time.
Arthur has a number of superhuman abilities. Unlike the original Aquaman, this is due to the experimental procedure he has undergone and not due to his royal Atlantean / human heritage.
Arthur has shown he is strong enough to break free from iron shackles and overpower metahuman Vandal Savage, although the full extent has not been revealed.
Superhuman Speed (Swimming)
Arthur has shown he possesses superhuman swimming speed when he caught up and leaped on a speeding plane.
Although Arthur hasn't exhibited the level of invulnerability Aquaman possesses, he was able to withstand a point blank bomb explosion that took out a building floor.
Arthur can function normally underwater and is able to withstand the high pressures and extreme temperatures of the deep, due to the experiment that he has undergone.
Arthur possesses enhanced vision, able to see at the bottom of the ocean
Arthur is not able to command fish as well as the original Aquaman, but he can see through their eyes, as well as talk to any creature living underwater.
Arthur has been trained by King Shark and the Dweller in the Depths in combat and particularly swordsmanship.
Weaponry & Equipment
He wears one of Aquaman's old spare chain male armored shirts.
Arthur carries an Atlantean sword. So far nothing special has been revealed about it.
Unlike the original Aquaman, Arthur needs hydration and will grow weaker the longer he stays out of water.