I have an idea about a lake which moves via erosion (and transferring said erosion to the other side to fill in the "hole" left by its advancement) and is slowly creeping towards a city that is polluting it. Its largely inspired by this picture of Lake St. Clair during an Algae Bloom.
I may alternatively remove the lake away from a population center and simply have it as a far off lake that is slowly getting closer.
Current plans for this include:
-said advancing lake.
-shipwrecks or industrial (polluting) ships occurring throughout the lake.
-a short message at the end made with wreckage.
What are your thoughts? Does this idea hold water?