A lot has to go right with a film for it to have a tagline this good:

The Day of the Dolphin – Unwittingly, he trained a dolphin to kill the President of the United States

The Day of the Dolphin at Wikipedia, at IMDB.

Neither a critical or commercial success on its release in 1973 (six years after Mike Nichols directed The Graduate, and two after George C. Scott turned down the Best Actor Oscar for Patton), this tale of espionage and talking dolphins was originally going to be directed by Roman Polanski: he was scouting for locations for the film when his wife Sharon Tate was brutally murdered by the Manson Family.