James Wan has a great working relationship with Warner Bros. and their subsidiary New Line Cinema. For the last several years, Wan and New Line have been building the "Conjuring universe" together, making CONJURING movies and then giving supernatural entities introduced in those movies their own spin-offs (ANNABELLE, THE NUN, etc.) Wan recently directed the DC Comics adaptation AQUAMAN for Warner, and the fact that his superhero movie is now getting a horror spin-off surprised me at first, but once the idea sank in I thought, "Of course they're doing that."
The Hollywood Reporter broke the news that Warner Bros. has hired screenwriters Noah Gardner and Aidan Fitzgerald to write a horror script based on
the Trench, the deadly amphibious creatures seen attacking the hero and his love, Mera, in Aquaman.
This horror project, appropriately titled THE TRENCH, will be produced by Wan and Peter Safran, and will be "much more modestly budgeted than the normal DC superhero tentpole". Presumably because it wouldn't be a superhero story. The main cast of AQUAMAN are not expected to show up. That would be pretty strange, to get a horror movie about the Trench monsters attacking people, then Aquaman arrives at the end to tell the monsters, "Hey, get away from there!"
THR notes that
the Trench creatures are rather recent arrivals to the Aquaman lore, having been introduced in the comics only in 2011 when DC did a revamp of its entire publishing line. They are revealed to be part of the kingdom of Atlantis but when it sunk, inhabitants who were cut off from other survivors and evolved into ravenous monsters.
James Wan responded to talk of THE TRENCH with a tweet that basically confirms that the project is happening, even if he says he's not confirming it.