The Day of the Dolphin

The Day of the Dolphin is a 1973 American sciencefiction thriller film directed by Mike Nichols and starring George C. Scott. Loosely based on the 1967 novel Un animal dou de raison A Sentient Animal, by French writer Robert Merle, the screenplay was written by Buck Henry.

The film version was originally going to be directed by Roman Polanski for United Artists in 1969, with Polanski writing the script. However, while Polanski was in London, England, looking for filming locations in August 1969, his pregnant wife, the actress Sharon Tate, was murdered in their Beverly Hills home by disciples of Charles Manson. Polanski returned to the United States and abandoned the project.The following year it was announced Franklin Schaffner would make the movie for the Mirisch Corporation. These plans were frustrated and Joseph Levine ended up buying the project from United Artists for Mike Nichols. ........

Source: Wikipedia