Survey markers on the ceiling of the drift. Water appears to be entering the system through the ceiling here. The redwall tends to act as an aquifer (hence the waterfalls shooting straight out of the cliffs formed by this layer), so this isn't really all that surprising.
Down under the water here is a shape that, at least in person, looked a lot like a hatch to me. I doubt it would have been waterproof though...
Some leftover wire in the drift. There is a series of these supports working back into the tunnel. Probably supported a power line for lighting.
