Considering how 'Aquaman' is now a billion-dollar movie, you can't be surprised that Warner Bros. is keen to make more movies.
What's surprising, however, is that they're making a spin-off not out of a character as is normally the case, but a movie's location. 'The Trench' will be the first follow-up to 'Aquaman' and is described by THR as "horror-tinged".
Currently, neither Jason Momoa nor James Wan are attached to star or direct and only the writers - Noah Gardner and Aidan Fitzgerald - are attached so far. As well as this, THR's report also states that the budget for 'The Trench' will be significantly less than the norm for comic-book blockbusters.
This likely means that 'The Trench' will be R-rated or will not marquee names like 'Aquaman' had. No release date has been set as of yet.