Orson Scott Card wrote the novelization of James Cameron's The Abyss while on-set during filming, since it was filmed in an abandoned nuclear reactor cooling to

Orson Scott Card wrote the novelization of James Cameron's The Abyss while on-set during filming, since it was filmed in an abandoned nuclear reactor cooling tower in his home state of South Carolina, and had some input on the script during shooting. (I heard this from Card at a science fiction convention, and it's borne out by IMDb trivia.)