David Kane has been a pirate for a while now, opposite his father, Jesse. The two have been working with Orm Marius to storm a submarine and take it over. What David does not know is this will be the last mission he goes on with his father. Upon Arthur Curry’s takeover of the submarine and rescue of the crew, he comes face-to-face with David and Jesse. At first, David is excited to take on the revered Aquaman. He believes the two were bound to meet at some point because of their overarching commonalities. However, once Jesse fires a weapon at Aquaman, he responds in kind. As the latter attempts to leave the ship, Jesse fires another weapon at him, causing a piece of the ship to collapse on him. This is the penultimate moment for Aquaman’s future foe. It’s where he makes the wrong decision: he chooses not to save David’s father.
This results in what begins a great hatred David has for Aquaman. You can see it fester in his eyes and face as his father kills himself. His father’s suicide by letting off an explosive device causes him to be even angrier because Jesse does it to push David to seek vengeance against Aquaman. This is the father telling the son to seek out your enemy and eliminate them. There’s a certain corruption that befalls the character of David Kane, as he begins his gradual transformation into Black Manta. Not only hearing the story of the United States turning their backs on his grandfather but seeing the death of his father, which he attributes to Aquaman, leads directly into David becoming ever more focused on defeating Aquaman.
Throughout the film, David does not seek out a black shaker but solidifies a stronger partnership with Orm than had been previous. He wants to get as much knowledge about Atlantis and where he can find Aquaman as possible. He does not seek any other recourse other than vengeance throughout the film. Eventually, Orm offers him new Atlantean technology and armor as well as his own commandos to hunt down Aquaman and Mera in Sicily, Italy. This is the first test of David as Black Manta. He tells Aquaman this is his name now and what to call him by rather than simply “the guy from the sub,” as Aquaman remembers him.
This comes also before a fully transformed Arthur Curry into Aquaman. That is to say, David Kane becomes Black Manta because of the actions of Arthur Curry before he finds King Atlan’s trident and takes the throne of Atlantis as Aquaman. While he is referred to as Aquaman in the film by others around him, it’s not until the ending of the movie that Arthur Curry accepts the title and his birthright in life. He does not seek a black shaker. While his is a positive, Kane’s anger toward Aquaman continues to grow throughout the film. There is no stopping him at this point. He has become Black Manta and seeks vengeance against anyone who gets in his way.
There’s no chance for him to stop his reign of terror. He has begun his work against Aquaman. While he is defeated in this film, Dr. Stephen Shin finds him and nurses him back to health. When Black Manta wakes up, he is no longer David Kane. He is fully Black Manta and ready immediately to begin hunting Aquaman once more. The deal the two strike is Manta will take Shin to Atlantis but Shin has to help him find Aquaman. We will see more of how this relationship progresses in the sequel but it leaves us simply with the truth: David Kane is no more. Black Manta has taken over.