According to The Hollywood Reporter, McG is still directing 20,000 Leagues Under the Sea: Captain Nemo but it has a new writer.
It turns out that Justin Marks will be rewriting Bill Marsilii's script of the Disney adventure.
Marks will apparently flesh out "the deep-sea universe" from the 1954 film. The original film was an adaptation of the Jules Verne novel. Marks apparently only has one month to work with McG and the craft designers on the film.