Article source of photo above
When one considers that our sewer systems run beneath our cities, allowing a passage of anyone who is desperate to not be seen but wants to go from point A to point B, that should aliens be among us, this might be their method of transportation.
This doesn't just apply to a potential alien underground network, but use by others including Bigfoot and creatures that may not have been identified that benefit from life in such an environment. You may never think about what's under your feet the same way again!
Remote control sewer cameras help to see if there are issues underground, but can also capture some, well, unusual findings (above). In this case, likely worms looped together and writhing.
Yes, cameras in the sewers capture things, sometimes things they need to go back and look at again....
Who is living in the sewers?
Lost rivers in England -
Bucharist Sewer Children