That, along with Momoa calling Patrick Wilson “King Orm” in an Instagram post, indicates that when we meet Orm in Aquaman, he’ll already be ruling Atlantis.
Following in the New 52’s footsteps, the DCEU’s Orm will share the same mother as Arthur Curry, Queen Atlanna, making him fully Atlantean.
Ocean Master’s real identity is simply Orm.
While we still don’t know exactly what Aquaman’s origins are in this cinematic universe, Temuera Morrison being cast as Thomas Curry suggests that like his comic book counterpart, Arthur Curry grew up with his human father on the surface.