A cursory search online would reveal tons of sites dedicated to compiling clips from various sources of girls drowning in quicksand, and then there are the niche video sites dedicated to providing original content (there probably is a booming industry in quicksand pit installation these days). On those sites, elaborate storylines are created to justify how these lovely ladies came to be trapped in the unforgiving, bottomless pit of certain-yet-sexy death.
It starts with the cable guy showing up to fix her box and ends with him pulling her to safety with a length of co-ax.
So ... maybe the quicksand thing triggers some "damsel in distress" response in the brain's boner cortex? If there's anything lonely Internet tough guys love, it's sitting behind their keyboards visualizing all the many ways they would totally jump in and save the unfortunate lady fake drowning in a boggy marsh. But the fact that they're jerking off to the "trapped and terrified" part, rather than the sexy rescue, really puts a darker spin on the whole thing. We'd prefer not to think any more about it.
We prefer our mud with a lot more "wrestle."