Zephyr, as you get lowered down, the light shrinks to an ever shrinking circle above, the interior of the stone walls almost immediately growing cooler than the warming desert above. As you go deeper, probably a few hundred feet now, the air starts to take on a more humid feel, and you start to notice a whiff of decay. You can't quite make out the water level just yet.
((Are you working out any signals with the group ahead of time?))