Quicksand Fans

I think that's where it was, anyway. The B&W scene in question was a guy was chasing a woman along a lake and she fell in and started sinking in the quicksand and he made her confess and when she confessed he told her "You can't sink any further. There's concrete at the bottom."
Anyone know what movie/TV show it was from?

That was on one of Dave's old clip tapes.

As I recall, it was not even quicksand, and she didn't real sinking. She was just standing waist deep in the water.

She thought she was sinking though. Does the clip come from any movie anyone remembers?

I think this is the movie you are looking for.
Highway Dragnet @
1954 B&W - Richard Conte, Joan Bennett, Wanda Hendrix
An ex-Marine is accused of murdering a former Las Vegas model. He escapes the police and hitches a ride with a magazine photographer who, by coincidence, is the one who killed the model because the model had earlier caused the suicide of her husband. The woman, wearing a white dress, is pursued by the guy along the shoreline and out onto a rickety walkway which collapses. She falls into the water and gets stuck in the quicksand underneath. With the cops within earshot, he gets the murder confession out of her as she sinks only to her waist after hitting the concrete bottom.

Excellent. Thank you!