What's going on with the pinky/purple lighting?
The cave was used as a film set in 2017 for “City in the City” (I think).
This passage had sandbags laid in the “trench” (to allow easy walking) and high volume water pumps at the top, so the passage could be “flooded” at the press of a button, this allowed the hero to rescue his damsel.
I think a cave diver tried to bring an electric cable in from the bottom via the sump but was unsuccessful so it was wedged into the passage sides out of sight.
We were “cave safety”, an interesting couple of days.