Aquaman director James Wan has cast Watchmen actor Patrick Wilson as Orm Curry aka the evil half brother of Aquaman who becomes the villain Ocean Master. Wilson has worked with Wan before on Insidious and the Conjuring franchise. So not only has he worked with DC Films and Warner Bros. director Zack Snyder bit he also has a strong history with Wan himself.
This is what you would call a perfect fit. Also to note Patrick Wilson was also in Batman V. Superman: Dawn of Justice as the voice of the President of the United States.
While its been rumored for a very long-term that Black Manta was going to be the main villain of Aquaman, it now seems the Ocean Master will play a large role as well.