To hear a quicksand fan describe his interest can be unnerving: Many describe what amounts to a sexual fascination with helpless women flailing for their lives. But there's more to the fetish than a bondage fantasy. For some, the excitement hinges on a damsel-in-distress melodrama with a heroic rescue. The mythology of quicksand can be just as inspiring on its own terms—conveying a nostalgia, erotic or not, for old-time serials and wilderness tales. One member of the community, "Crypto," describes feeling a sexual attraction to the quicksand itself, as opposed to whoever or whatever happens to be trapped in it. He doesn't care whether the victim is male or female, human or animal. (As a little boy, he was drawn to a scene from the 1960 Disney film, Swiss Family Robinson, in which a zebra sinks into a mud bog.) "It is the quicksand alone that is the trigger for the sexual response," he explains over e-mail. "It is just the way I am wired genetically, I guess."...