The film's plot was very difficult to develop. and admitted that the film didn't have a script when it went into production. They just had the major action sequences planned out when they started filming. For instance, the underwater heist sequence was outlined from beginning to end, but what was actually stealing was unknown while they were filming it. Some scenes of important exposition were written while they were being filmed. Drew Pearce was originally hired to pen the script, when the film was announced in August 2013, but was replaced by Will Staples in May of 2014. Staples was then let go when production began that August and took up writing duties while filming, with the previous scripts seemingly being largely ignored, or thrown out. Production had to be halted in February 2015, so that and could re-work the film's story and ending. It is unknown how much Pearce and Staples had written for the film, or how much of their content made it into the final film, but Pearce was acknowledged for the story, and is credited as the Screenwriter.
The terminal in the underwater safe that needs to access is 108. This number has cropped up in most productions, perhaps most famously in Lost (2004), where it was the sum of the infamous number sequence (4, 8, 15, 16, 23, 42).