Not Gilligan's Island: Texas man killed by quicksand on the San Antonio River

[Metaphorical]

4. It's also worth noting

that quicksand tends to form in flash flooding situations, where water does not have the opportunity to drain naturally. This adds slow moving currents to the mix. More than likely, what did the guy in was getting caught up in the flash flood then inhaling the silt laden muddy water. Parts of Colorado, where I have friends, are very similarly - very dry most of the time, but flash floods can turn deadly there quickly.