OK, I found it from looking up Glynis Johns on IMDB. It's called The Chapman Report. This is Glynis above with, I believe Ty Hardin. IMDB doesn't name a specific filming location for the beach scenes, but they list all of the filming locations to be in Southern California, though the film takes place outside of San Francisco. So I wonder where this beach was.
The film's largely forgotten, though there's a lot of pedigree behind it. It's based on an Irving Wallace novel, inspired by The Kinsey Report, and it's detailing of the sex lives of 4 women. It was directed by George Cukor, Leonard Rosenman the score, Orry-Kelly the costumes and was produced by Richard F. and Darryl D. Zanuck.
And it has a lot of well-known people in the cast -- Claire Bloom, Jane Fonda, Shelley Winters, Glynis Johns (these 4 women each have a sexual hangup in the film ranging from frigidity to nymphomania). There's also Efrem Zimbalist Jr., Ray Danton, Ty Hardin, Andrew Duggan, John Dehner, Chad Everett, Cloris Leachman, Lesley Anne Warren (a young child) and Roy Roberts. Harold J. Stone is also in the film, a character actor you'd definitely recognize from dozens of movies and TV series. He got a Supporting Actor Golden Globe nomination for this movie. So did George Cukor (Director) and Glynis Johns (Best Actress). The film also did for Best Film - Drama.
The film is also in color, by the way.