Old radio drama featuring Tarzan. Essentially, there's quicksand below the suspension bridge. Bad guy pushes Tarzan off bridge at the 17 minute mark, he is rescued at the 20:32 minute mark. The bad guy gets it starting 22:58. Not a lot of description or sound effects, but cool nonetheless.
https://www.youtube.com/watch?v=7GrU7oxchSQ
I read somewhere The Shadow radio series has at least one quicksand scene in it... but that does cover a lot of territory... Hopefully, I'll find a clue to lead me to it.
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