quicksand

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A bed of loose sand mixed with water forming a soft shifting mass that yields easily to pressure and tends to engulf any object resting on its surface.
2. n. A place or situation into which entry can be swift and sudden but from which extrication can be difficult or impossible. Often used in the plural: "This theory of the future entrapped [them] in the quicksands of Vietnam” ( Arthur M. Schlesinger, Jr.)

Century Dictionary and Cyclopedia

1. n. A movable sand-bank in a sea, lake, or river; a large mass of loose or moving sand mixed with water formed on many sea-coasts, at the mouths and in the channels of rivers, etc., sometimes dangerous to vessels, and especially to travelers.
2. To catch in a quicksand.
3. To cover with quicksands: as, a quicksanded coast.

Wiktionary

1. n. Wet sand that things readily sink in, often found near rivers or coasts
2. n. Anything that pulls one down or buries one metaphorically

GNU Webster's 1913

1. n. Sand easily moved or readily yielding to pressure; especially, a deep mass of loose or moving sand mixed with water, sometimes found at the mouth of a river or along some coasts, and very dangerous, from the difficulty of extricating a person who begins sinking into it.

WordNet 3.0

1. n. a treacherous situation that tends to entrap and destroy
2. n. a pit filled with loose wet sand into which objects are sucked down