First, let's dispense with the movie myth: Man running through jungle blindly stumbles into pit of quicksand; within seconds he is sucked under by a powerful vacuum, leaving behind only a floating pith helmet as a warning to others.
The horror! Say it isn't so.
It isn't so.
You're Not Going Under
Research shows that it's impossible for a person to become completely submerged in the stuff. That's because the human body is less dense than quicksand - a mixture of sand, clay and salt water. The worst that could happen is that you could sink in to just above your waist.
Not that waist-deep in quicksand is a particularly good place to be ... If your feet become wedged in the densely packed sand at the bottom, it's very hard to get them out. When people die in quicksand, they don't suffocate. They die of thirst or starve, or if they're near a coast, they drown in high tide.
So how do you get out? To begin with, if you know you'll be in an area where there may be quicksand - marshes, tidal pools - remember Teddy Roosevelt's mantra: "Walk softly and carry a big stick." Walking softly is sensible, but it's the big stick that could save you.
Float, Don't Kick, to the Top
If you fall into quicksand, resist the natural instinct to kick your way out. That just separates the sand from the water, forming a very dense layer of sediment at bottom where your feet are. Instead, you need to stay calm and lean back, so you get as much of your body surface on the water as possible. That's where the big stick can help; if you can place it under your back and perpendicular to your body, it can help you float.
As you begin floating, slowly start moving your feet - not in a thrashing motion, but in small circles, the point being to get more water down into the thick sediment where your feet are. It may take awhile, but in time, as you get more of your body on the water's surface, you should be able to float free and paddle your way to solid ground.
Information courtesy of the U.S. Army Survival Manual