In the dream, I heard a woman describe a nearby body of water as too polluted to swim in. At that moment, I found myself standing on a rectangular concrete block a bit more than two square feet. This block was barely covered by water, although, somehow, my feet (socks, no shoes) were not wet. I was standing in the aforementioned polluted body of water, which appeared to be a reservoir. The block was part of a wall or walkway that formed a semicircle curving off to a point to my right about a quarter mile away. I realized I had to walk along the top of this wall to that distant point without falling into the polluted water. I walked, mostly confidently, nervous a few times.
Suddenly, there was an upheaval like a wave and the wall/walkway surged to the right. "It moves?!," I cried out loud with some exasperation. Somehow, I did not spill from my footing even as the wall swept to the right, toward the edge of the reservoir. This edge had a chain link fence atop another wall. I considered that I might be better off crawling along that wall, clinging to the fence, than taking my chances with the movements of the wave-wall.
The wall I was standing on began to move back, as if with a retreating wave and I decided to jump to the fence-wall. I fell into the water but scrambled out. I realized I might be worse off, because this wall had a very narrow ledge I had to stand on while clinging to the fence, but I had no other choice at this point.
I slid along the ledge, clinging to the fence. In places, the wall had pillars I had to squirm around.
In a few places, spiders had nests. These spiders were large, dull-black, and squarish, like badly drawn black widow spiders. I had to watch my movements even more closely as I maneuvered around the spiders.
Eventually, I arrived at a wall that was 90 degrees to the fence. I worked my way around the wall and the last spider. Around one corner I encountered three other people, stuck in similar circumstances. The farthest of the three could not go on, frozen with despair or fear. How was I going to get around this new roadblock?
I took the hand of the person closest to me and leaned away from the wall, my feet still on the narrow ledge. Like a pendulum, I swung out and around the other people and came back to the wall beyond the immobile one. This so delighted them all that hope was restored and I woke up.