Anacondas are large snakes that can eat people, so the simile is saying that the darkness was so thick that it felt like it could consume them
Consider the statement "We were walking through a New England forest and the darkness was barely present, due to the thick canopy of trees that were spaced so impossibly close together.". Based on this "But on top of that, we were wandering through some new england forest and the thick canopy of trees, spaced so impossibly close together, made the darkness feel like like a man-eating anaconda ." a true statement? Yes, no, or I don't know?