Most of the shots in Erased its opening are references to events events or cryptic imagery like when Satoru's refers to himself as Grim Reaper that tries to put things back the way they were, but the more he acts the more other people involved suffer (see the last bit in episode 6).
However at around 37 seconds into the opening this shot of a large amount of water in the school shows up. I don't remember this happening in the anime.
What is the meaning of this shot? Does it bear a cryptic message to something in the show?