John D. MacDonald's "The Deep End" (1964).

A woman taking a swim ends up dead, and a PI (Clu Gulager) questions the conclusion of accidental drowning or suicide. The source for this 1964 episode of Kraft Suspense Theatre, although the credits merely state "based on a book by John P. [sic] MacDonald," is likely The Drowner by John D. MacDonald (Cosmopolitan Jan. 1963; novel 1963). Aldo Ray, Ellen Burstyn, Tina Louise, and Whit Bissell costar. The music for the episode is by John Williams.