Felicitas mine in northern Germany, flooded very unexpectedly, and is full of abandoned mining equipment

https://www.facebook.com/photo/?fbid=4246194485600331&set=a.1652036835016122

https://divernet.com/scuba-diving/a-tale-of-two-mines/

https://xray-mag.com/content/felicitas-mine

https://minediving.de/locations/felicitas-germany/