What a hard character to do right. So many mines to avoid, so much dumbess to omit, yet there are huge stories there waiting to be told with a powerful hero at the center.
I’d like to see them kinda flip the Ocean Master story-line. I know this messes with the details of established story, but I think it’s a stronger way to hit the same mythic notes notes with a less recycled and boring plot.

Arthur Curry was raised on land, but had always been drawn to the sea. By the time our movie starts, he’s already naturally discovered the basics of his powers and through them, found Atlantis. There he learned that his mother, who died while he was very young, was princess; twin sister to the current king. Like any sane person would, he’s been spending most of his time in Atlantis, because there he’s second-tier royalty. This is NOT explained in voice over, it’s just where the movie starts, and all this info is doled out gradually over the first act.

First Act:
The action starts when an assassin keeps trying to kill Arthur. This is Black Manta, a radical who wants to wage war on the surface, who is assumed to want to kill Curry for his half-human heritage. His cousin the crown-prince gives him all the protection he can, assigning a security detail led by the king’s personal bodyguard, Mera. Obviously, there’s sexy-eyes between her and her new charge, but she’s too dutiful to do anything with that.
The attempts continue, and innocent bystanders die instead of the intended target. The ailing king explains that Curry’s choices are either to live in Atlantis under such security as to make him a virtual prisoner, or to return to the surface. After a few days under protective custody, he returns to the surface.

Second Act:
Back on the surface, Arthur is pretty bummed about boring mundane life. He tries to take advantage of his talents, but without revealing his powers and origin, and thus the existence of secretive Atlantis, he can’t get a good job doing much worthwhile because he has no regular qualifications. He can’t even go near the ocean for fear of assassination.
A year later, he’s visited by an Atlantian messenger who informs him of his uncle the king’s death, but warns him that the Crown Prince has changed- grown in power and becoming increasingly hostile to the surface. This is just before the courier’s killed by Black Manta. Arthur barely escapes with his life.

Act Three:
Manta starts tearing up the surface world looking for Curry, and in desperation Arthur eventually decides he must stop hiding and face Manta to end the destruction. They duke it out in Coast City, and while Aquaman saves many lives, he nearly loses his own. He’s saved at the last minute by a small cadre of Antlantian commandos led by Mera. As they rush Arthur’s battered body away from the scene, he hears Black Manta declare that it doesn’t matter- no surfacer will ever sit the throne of Atlantis, and soon there will be no surfacers to do so!

Mera explains to a recuperating Arthur that after the king died, his son’s increasing belligerence started to worry many, including herself. As he riled the population to anger against the surface, she started researching Arthur Curry and the royal line. It turns out that Arthur’s mother was the older of the twins, and their father had lied to keep a king on the throne rather than a queen, even sending his own daughter into exile where she died. This makes Arthur Curry the rightful king. He says it doesn’t matter, it’s none of his business now, and he’s not qualified: reasons, reasons, reasons. But Mera tells him that now Atlantis is mobilizing for war against the surface. Aquaman vows that he’ll take the throne if that’s what’s necessary to keep both his people from destroying each other in war against each other.