Ladybower is a large reservoir in Derbyshire, UK. Two villages were flooded to fill the reservoir, and when the water level is low, the ruins become accessible.
This guy has posted a bunch of videos looking around, and this week the level has dropped even further revealing even more.
It is very muddy - though judging by the footprints, people haven't let that stop them explore.
I only wish I could explore the mud, too.